COSMO-15, the 19th annual International Conference on Particle Physics and Cosmology

Europe/Zurich
Warsaw, Poland

Warsaw, Poland

University of Warsaw, 26/28 Krakowskie Przedmiescie Street in the building of the Old Library
Description

COSMO-15 webpage: http://cosmo15.ncbj.gov.pl/

 

Starting as a workshop in Ambleside in 1997, annual COSMO meetings rapidly became a major venue of interaction of theorists working at an interface of particle physics, astrophysics and cosmology.

    • 08:00 09:00
      Registration 1h Lobby ()

      Lobby

      Reception desk will be opened during the whole conference.

    • 09:00 10:25
      Plenary Main Hall ()

      Main Hall

      Convener: Carlos Martins
      • 09:00
        Welcome and introduction 10m
        Speaker: Leszek Roszkowski (National Centre for Nuclear Research, Poland)
      • 09:10
        Opening address 5m
        Speaker: Grzegorz Wrochna (National Centre for Nuclear Research, Poland)
      • 09:15
        Recent advances in astrophysics of cosmic rays and gamma-ray astronomy 35m
        Speaker: Igor Moskalenko (Stanford University, United States)
      • 09:50
        How to learn to love the BOSS (Baryon Oscillations Spectroscopic Survey) 35m
        Speaker: Shirley Ho (Carnegie Mellon University, United States)
    • 10:25 10:55
      Coffee 30m
    • 10:55 12:40
      Plenary Main Hall ()

      Main Hall

      Convener: Jun'ichi Yokoyama
      • 10:55
        The Mysterious Neutrinos - Clues from Astrophysics and Cosmology 35m
        Speaker: John Beacom (Ohio State University, United States)
      • 11:30
        Leptogenesis and Flavour Models 35m
        Speaker: Stephen King (University of Southampton, United Kingdom)
      • 12:05
        Vacuum (meta?)stability and Higgs inflation 35m
        Speaker: Mikhail Shaposhnikov (EPFL, Switzerland)
    • 12:40 14:00
      Lunch 1h 20m
    • 14:00 15:45
      Plenary Main Hall ()

      Main Hall

      Convener: John Beacom
      • 14:00
        Perspectives of discoveries in intergalactic space 35m
        Speaker: Matteo Viel (INAF OATs, Italy)
      • 14:35
        Numerical simulations of large scale structure: overview and outlook 35m
        Speaker: Debora Sijacki (University of Cambridge, United Kingdom)
      • 15:10
        Overview of WIMP Dark Matter 35m
        Speaker: Katherine Freese (Nordita, Sweden and University of Michigan, United States)
    • 15:45 16:15
      Coffee 30m
    • 16:15 18:00
      Plenary Main Hall ()

      Main Hall

      Convener: Stephen King
      • 16:15
        Beyond the thermal WIMP dark matter 35m
        Speaker: Ki-Young Choi (KASI, Republic of Korea)
      • 16:50
        Direct Searches for WIMP Dark Matter 35m
        Speaker: Marc Schumann (University of Bern, Switzerland)
      • 17:25
        The battlegrounds of gamma-ray detection of dark matter: the Galactic Center and dwarf galaxies 35m
        Speaker: Miguel Sanchez-Condé (Oskar Klein Centre and Stockholm University, Sweden)
    • 19:00 21:30
      Welcome Reception 2h 30m BrowArmia, Warsaw

      BrowArmia, Warsaw

    • 09:00 10:10
      Plenary Main Hall ()

      Main Hall

      Convener: Matts Roos
      • 09:00
        Indirect Searches for Particle Dark Matter 35m
        Speaker: Torsten Bringmann (University of Oslo, Norway)
      • 09:35
        Viscous dark matter 35m
        Speaker: Nikolaos Tetradis (University of Athens, Greece)
    • 10:10 10:40
      Coffee 30m
    • 10:40 12:30
      Plenary Main Hall ()

      Main Hall

      Convener: Eric Linder
      • 10:40
        Recent CMB results from Planck 35m
        Speaker: Anthony Challinor (University of Cambridge, United Kingdom)
      • 11:15
        Large scale structure of the Universe: the angular power spectrum and bispectrum 35m
        Speaker: Ruth Durrer (Universite de Geneve, Switzerland)
      • 11:50
        General Relativity: its creation, classical tests and new effects in rotating systems 35m
        Speaker: Edward Malec (Institute of Physics Jagiellonian University, Poland)
    • 12:30 14:00
      Lunch 1h 30m
    • 12:30 13:30
      Poster Session
      • 12:30
        Aspects of topos theory in cosmology 1m
        We use the 'local weakening of logic in a spacetime' as a mathematical tool suitable also for building cosmological models. The models extend the regular spacetime solutions of Einstein equations towards solutions with certain spacetime singularities. Such models are also natural for addressing the renormalization questions of various quantum field theories. We discuss this issue briefly. There exist several weak logics; here we deal with the internal logic of a smooth topos B of sheaves on a site, constructed by Moerdijk and Reyes. The weakening of logic gives rise to the indistinguishability of the standard real line and the reals internal to B, allowing for the shift between them, being the core of various physical effects. Thus the approach is another example of the use of topos theory in physics, this time in cosmology.
        Speaker: Krzysztof Bielas (Institute of Physics, University of Silesia, Poland)
      • 12:31
        Constructing N-body Simulations with General Relativistic Dynamics 1m
        N-body simulations normally use equations of Newtonian dynamics to evolve particles and fields forward in time. On galactic scales and at times late enough for velocities and gradients of fields to be small this turns out to be an extremely good approximation. However, in modified gravity models, at earlier times when neutrinos are relativistic, or on much larger scales, evolving relativistic sources become important. Therefore, nonlinear evolution of cosmic structure requires a more sophisticated modelling of dynamics. We model general relativity numerically with a weak-field approximation, but still allow for large gradients of the fields and relativistic velocities for the particles. This makes the system much more complicated. In this work, we therefore simplify the system by considering a one-dimensional, spherically symmetric setup. Apart from just reducing the complexity, this setup also allows us to model spherically symmetric fluctuations such as a void or a spherical halo.
        Speaker: Mateja Gosenca (Astronomy Centre, School of Mathematical and Physical Sciences, University of Sussex, United Kingdom)
      • 12:32
        Lambda Units and Lambda Quantum of Action have they any physical sense 1m
        The Lambda Units determined by three Einstein's constants: velocity of light, his gravitational constant and his lambda cosmological constant will be introduced. Some of them are already used in relativistic cosmology e.g. lambda density of mass and the pressure of the physical vacuum . Other Units like e.g. lambda quantum of action i.e. the inverse of the product of the mentioned above three Einstein's constants and also lambda charge i.e. the square root of the product of lambda quantum of action and the velocity of light are not yet used. Their physical meaning will be looked for. Have they any part to play in the theory of dark energy? That's what has to be investigated.
        Speaker: Ludwik Kostro (Ateneum-University in Gdansk, Poland)
      • 12:33
        The local effect of Dark Energy on the evolution of galaxy clusters: the formation of massive structures in the cluster centre 1m
        In this contribution we discuss how the centres of galaxy clusters evolve in time, showing the results of a series of direct N-body modelling at high resolution. In particular, we followed the evolution of a galaxy cluster with a mass of around 10^14 solar masses in four different configurations: 1) isolated cluster; 2) cluster subjected to the action of Dark Energy; 3) cluster composed of galaxies and gas; 4) cluster composed of galaxies and gas subjected to the action of Dark Energy. The dynamical evolution of the system leads in all the cases to the formation of dense and massive substructures in the cluster centre, whose properties depend slightly on the kind of environment in which the cluster evolve. Indeed, these substructures form in consequence of a series of collisions and merging among the galaxies that move in the innermost region of the cluster under the action of the dynamical friction. In our contribution, we investigate how the structural properties of the merging product depends on the main characteristics of those galaxies that contributed to its formation and, moreover, to the effects induced by the environment in which the cluster evolves.
        Speaker: Manuel Arca Sedda (University of Rome La Sapienza, Italy)
      • 12:34
        General formalism for bigravity perturbations 1m
        We introduce a new formalism to study perturbations of Hassan-Rosen bigravity theory, around general backgrounds for the two dynamical metrics. In particular, we derive the general expression for the mass term and we explicitly compute it for some cosmological settings. We study in detail tensor perturbations in branch-one bigravity using this formalism. We show that the tensor sector is affected by a late-time instability, which sets-in when the mass matrix becomes not positive definite.
        Speaker: Giulia Cusin (Département de Physique Théorique and Center for Astroparticle Physics, University of Geneva, Switzerland)
      • 12:35
        Revisiting f(R) cosmology 1m
        We introduce a different approach in f(R) gravity. Our approach avoids the mapping to scalar tensor theories using the Ricci scalar itself as an 'extra' degree of freedom. In this talk we will present this formalism and we will analyze the equation of state (EOS) of the geometric dark energy related with the extra terms in f(R), including the comparison of several EOS that have been proposed in the past. Finally we will show how some models could be in a good agreement with the value of H measured by using Barionic Acoustic Oscillations.
        Speaker: Luisa Jaime (Institute for Theoretical Physics, Heidelberg University, Germany)
      • 12:36
        Cosmic acceleration with a negative cosmological constant in higher dimensions 1m
        We study gravitational theories with a cosmological constant and the Gauss-Bonnet curvature squared term and analyze the possibility of de Sitter expanding spacetime with a constant internal space. We find that there are two branches of the de Sitter solutions: Both the curvature of the internal space and the cosmological constant are (1) positive and (2) negative. From the stability analysis, we show that the de Sitter solution of the case (1) is unstable, while that in the case (2) is stable. Namely de Sitter solution in the present system is stable if the cosmological constant is negative. We extend our analysis to the gravitational theories with higher-order Lovelock curvature terms. Although the existence and the stability of the de Sitter solutions are very complicated and highly depend on the coupling constants, there exist stable de Sitter solutions similar to the case (2) in general. We also find de Sitter solutions with Hubble scale much smaller than the scale of a cosmological constant, which may explain a discrepancy between an inflation energy scale and the Planck scale.
        Speaker: Nobuyoshi Ohta (Department of Physics, Kinki University, Japan)
      • 12:37
        Bigravity from gradient expansion in DGP 2-brane model 1m
        Recently the ghost-free bigravity, the gravitational theory which contains two metrics interacting each other, is constructed by tuning the interaction terms to remove Boulware-Deser ghost. Using this model, we can realize the late-time cosmic accelerating expansion and the gravitational wave has a charasteristic feature. However, we have no idea what is the mechanism which tunes the interaction terms to the specific ones derived by the ghost-free condition technically. Therefore, we tried to derive the ghost-free bigravity as an low-energy effective theory of DGP 2-brane model. I will talk about the attempt to obtain a bigravity model by solving the bulk metric with the gradient expansion and how this bigravity model behaves compared with the ghost-free bigravity.
        Speaker: Yasuho Yamashita (Yukawa Institute for Theoritical Physics, Japan)
      • 12:38
        Corrections from the quantum sub-structure of the background metric 1m
        We follow the corpuscular approach proposed by Dvali and Gomez, in which N universally characterizes gravitational backgrounds (with N = (Mp)^2/Λ for de Sitter spacetime). In doing so, we explicitly draw a fully quantum picture of the background metric in the limit of weak gravity. Using coherent states in each mode, we show that it can be understood as collective effect of soft, gravitationally non-interacting gravitons. Furthermore, we derive that the motion in the curved spacetime can be naturally modeled as scattering off the constituent gravitons. Consequently, the back reaction, which is inaccessible in any semi-classical approach, immediately follows from the fact that the background has gained or lost constituents. We show that this back reaction leads to quantum corrections which scale like 1/N, as expected. Finally, we investigate a possible breakdown of the classical metric description due to decoherence effects.
        Speaker: Sebastian Zell (Department of Physics, Ludwig-Maximilians-Universitaet Muenchen, Germany)
      • 12:39
        Relativistic systems of Fermions with anisotropy and cutoff energy in their distribution function 1m
        Systems of selfgravitating Fermions constitute a topic of great interest in astrophysics, due to the wide range of applications, and are used also to explain dark matter in galaxies and clusters of galaxies. Here, we study the gravitational equilibrium of spherical models describing a semidegenerate collisionless gas. The Fermi-Dirac distribution function, modified by a cutoff term in order to avoid infinite solutions in mass and radius, is multiplied by an anisotropic term, depending on the angular momentum, evidencing the prevalence of tangential motion of the particles. The starting point is solving the equations of the gravitational equilibrium in General Relativistic regime and analyzing the behavior of the matter density through the calculation of the components of the pressure tensor. We have extended the analysis from non-quantum regime to fully degenerate limit, and we considered also the limits on the mass of particles composing the system.
        Speaker: Martina Donnari (Department of Physics, University of Rome La Sapienza, Italy)
      • 12:40
        Supersymmetric dark matter with low reheating temperature 1m
        I will examine the relic abundance of supersymmetric dark matter in a scenario where the reheating temperature T_R of the Universe after inflation is low, in the range of tens or of hundreds of GeV. To this end I will solve the Boltzmann equation during and after the period of reheating, taking into account cosmological as well as collider constraints, in particular the recent Higgs boson discovery. I will consider several candidates for the lightest supersymmetric particle (LSP) as a dark matter candidate. In the case of the neutralino LSP, large new regions of parameter space open up, depending on the value of reheating temperature. Heavy wino LSP, which has been ruled out in a standard high T_R scenario by indirect detection limits, becomes again viable. Gravitino and axino as dark matter will be also presented.
        Speaker: Sebastian Trojanowski (National Centre for Nuclear Research, Poland)
      • 12:41
        Sensitivity of CTA to dark matter annihilations in the galactic centre 1m
        We analyse the sensitivity of the future Cherenkov Telescope Array (CTA) experiment to dark matter annihilations in the galactic centre using the most up to date instrument response functions and background simulation model provided by the CTA Collaboration. We systematically examine the different statistical methods for setting limits using CTA and provide a realistic assessment of the sensitivity of CTA to photon fluxes from dark matter annihilation by means of a binned likelihood analysis for the Einasto and Navarro-Frenk-White halo profiles. Applying these projections to the phenomenological minimal supersymmetric standard model (pMSSM) we show that CTA is bound to exclude at the 95% C.L. almost all of the phenomenologically favoured ~ 1 TeV higgsino region of the pMSSM, effectively closing the window for heavy supersymmetric dark matter in many realistic models. CTA will be able to probe the vast majority of cases corresponding to a spin-independent scattering cross section below the reach of 1-tonne underground detector searches for dark matter. Altogether, CTA will provide a highly sensitive way of searching for dark matter that will be partially overlapping and partially complementary with 1-tonne detector and collider searches, thus being instrumental to effectively explore the nearly full parameter space of the pMSSM.
        Speaker: Andrew Williams (National Centre for Nuclear Research, Poland)
      • 12:42
        The end of the beginning: isocurvature modes in primordial black hole dark matter 1m
        Primordial black holes may have formed very early on during the radiation dominated era in the early universe, and are normally used to probe the small scale perturbations formed towards the end of inflation. I will present a method by which the large scale perturbations in the number density of primordial black holes may be used to place tight constraints on non-gaussianity if PBHs account for dark matter (DM). The presence of local-type non-gaussianity is known to have a significant effect on the abundance of primordial black holes, and modal coupling from the observed CMB scale modes can significantly alter the number density of PBHs that form within different regions of the universe, which appear as DM isocurvature modes.
        Speaker: Sam Young (Physics and Astronomy, University of Sussex, United Kingdom)
      • 12:44
        Inflation from radion gauge-Higgs potential at Planck scale 1m
        We study whether the inflation is realized based on the radion gauge-Higgs potential obtained from the one-loop calculation in the 5-dimensional gravity coupled to a U(1) gauge theory. We show that the gauge-Higgs can give rise to inflation in accord with the astrophysical data and the radion plays a role in fixing the values of physical parameters. We clarify the reason why the radion dominated inflation and the hybrid inflation cannot occur in our framework. Based on arXiv:1504.06905[hep-ph].
        Speaker: Yugo Abe (Shinshu University, Japan)
      • 12:45
        Evolution of density perturbations in inflationary models with two scalar fields and with different sound speeds 1m
        Equations of motion in slow roll inflationary models with two scalar fields for scalar perturbations metrics were analysed for an example of turning valley in scalar potential with non-canonical kinetic term. The impact of the multi-scale dynamics on the sub-horizon evolution of the perturbations was studied with a special emphasis on the (lack of) decoupling of the large scale modes and features of the background evolution. Potential consequences for the interpretation of the Planck data were discussed.
        Speaker: Lukasz Dulny (Faculty of Physics, University of Warsaw, Poland)
      • 12:47
        Avoiding the Higgs deflation 1m
        It has been shown that Higgs inflation could be realized even if the Higgs potential has a negative energy minimum separating the inflationary part from the low-energy SM regime. The precise shape of the potential is dictated by the running of the couplings which necessarily differs from SM predictions at high-energies. We explore how the high-energy running affects the details of the reheating state after Higgs inflation. In particular, we establish the conditions necessary for avoiding Higgs deflation: an anti de Sitter stage caused by the Higgs field trapped in the negative energy minimum after inflation. This places interesting constraints on the viable β-functions connecting the SM Higgs potential to the inflationary regime.
        Speaker: Vera-Maria Enckell (Department of Physics, University of Helsinki, Finland)
      • 12:48
        Particle production in the expanding universe 1m
        It is known that time-dependent vacuum expectation value of the background field causes the production of particles, in the expanding universe this process is also influenced by the time-dependence of the scale factor. Poster would present the general mechanism of particle production in time-varying backgrounds with the impact of rescattering emphasised, also in models with more than one coupling constant. Cosmological applications of this general method shall be presented.
        Speaker: Olga Czerwinska (University of Warsaw, Poland)
      • 12:49
        Field range bound and consistency in generalized G-inflation 1m
        We systematically show that in potential driven generalized G-inflation models, quantum corrections coming from new physics at the strong coupling scale can be avoided, while producing observable tensor modes. The effective action can be approximated by the tree level action, and as a result, these models are internally consistent, despite the fact that we introduced new mass scales below the energy scale of inflation. Although observable tensor modes are produced with sub-strong coupling scale field excursions, this is not an evasion of the Lyth bound, since the models include higher-derivative non-canonical kinetic terms, and effective rescaling of the field would result in super-Planckian field excursions. We argue that the enhanced kinetic term of the inflaton screens the interactions with other fields, keeping the system weakly coupled during inflation.
        Speaker: Taro Kunimitsu (RESCEU University of Tokyo, Japan)
      • 12:50
        Scale-invariant top condensate model as the solution to the hierarchy problem and its cosmological implications 1m
        TBA
        Speaker: Jie Liang (School of Physics, University of Sydney, Australia)
      • 12:51
        Hill crossing after hilltop inflation 1m
        In 'hilltop inflation', inflation takes place when the inflaton field slowly rolls from close to a maximum of its potential (i.e. the 'hilltop') towards its minimum. When the inflaton potential is associated with a phase transition, possible topological defects produced during this phase transition, such as domain walls, are efficiently diluted during inflation. It is typically assumed that they also do not reform after inflation, i.e. that the inflaton field stays on its side of the 'hill', finally performing damped oscillations around the minimum of the potential. In this paper we study the linear and the non-linear phases of preheating after hilltop inflation. We find that the fluctuations of the inflaton field during the tachyonic oscillation phase grow strong enough to allow the inflaton field to form regions in position space where it crosses 'over the top of the hill' towards the 'wrong vacuum'. We investigate the formation and behaviour of these overshooting regions using lattice simulations: Rather than durable domain walls, these regions form oscillon-like structures (i.e. localized bubbles that oscillate between the two vacua) which should be included in a careful study of preheating in hilltop inflation.
        Speaker: Stefano Orani (University of Basel, Switzerland)
      • 12:52
        Universality classes for models of inflation 1m
        In some recent papers it was proved that the cosmological evolution of a scalar field in a potential can be descirbed in terms of a renormalisation group equation. The slow rolling regime of the inflaton can be compared with the slow departure from a fixed point of the beta function in the RG group context. This can be seen as an effective approach to the problem in the sense that the perturbative expansion of the beta function close to the fixed point drives the reconstruction of the potential associated with the theory. This explains in part the universality observed in the predictions of a certain number of inflationary models. The nearly de Sitter geometry of the inflating universe can also be mapped into a corresponding anti de Sitter landscape that allows to discuss the topic in the context of the AdS/CFT correspondence. The holographic flow from the fixed point can then be naturally associated with the departure from the nearly AdS geometry. In this framework it is possible to reconsider some troblesome aspects under a whole different point of view that may suggest some new and intriguing interpretation.
        Speaker: Mauro Pieroni (AstroParticle and Cosmology laboratory, Paris Diderot University-Paris 7, France)
      • 12:53
        A Recipe for a Strong First Order Electroweak Phase Transition 1m
        Taking on a new perspective of the electroweak phase transition, we investigate a quantity called the one loop zero temperature vacuum energy difference. This quantity allows us to address all manner of features that are known to give rise to a strong first order electroweak phase transition. Our study is conducted using six extensions to the Standard Model of varying complexity, non-supersymmetric to supersymmetric in nature. We find there is a strong trend between the one loop zero temperature vacuum energy difference and the strength of the electroweak phase transition, subject to the vanishing of Higgs masses which ill-define the broken vacuum and avoid a strong first order phase transition. We suggest two recipes that guarantee a strong first order electroweak phase transition without the need for any finite temperature calculations.
        Speaker: Christopher Harman (University of Sussex, United Kingdom)
      • 12:54
        Gravitational waves from slow-roll inflation in Lorentz-violating Weyl gravity 1m
        We consider a squared term of Weyl tensor in the Einstein-Hilbert’s action. It is one kind of the theories about higher curvature invariants in the action as quantum corrections. In general, such additional terms generate ghost degrees of freedom. But the theory we consider here is ghost free by breaking local Lorentz symmetry. Using this theory, we consider gravitational waves from slow-roll inflation and calculate the power spectrum numerically. We compare the results with the study about de-Sitter expansion and the case of general relativity. Finally we consider gravitational waves from slow-roll inflation in standard Weyl gravity in which local Lorentz symmetry is not broken and there are ghost degrees of freedom.
        Speaker: Kohji Yajima (Department of Physics, Rikkyo University, Japan)
      • 12:55
        Model-independent constraints on modified gravity from current and future RSD and Supernovae Ia measurements 1m
        Most cosmological constraints on modified gravity are obtained assuming that the cosmic evolution was standard CDM in the past and that the present matter density and power spectrum normalization are the same as in a CDM model. Here we examine how the constraints change when these assumptions are lifted. We focus in particular on the parameter Y (also called G_effective ) that quanties the deviation from the Poisson equation. We obtain constraints on this parameter by using current RSD measurements combined with the measurements of the apparent magnitude of the Sn Ia, taken from the JLA catalogue. We also forecast the precision of a future estimation of Y for a Euclid-like redshift survey and for a SKA1 and SKA2 mission. We produce a forecast of a cosmological exclusion plot on the Yukawa strength and range parameters, which complements similar plots on laboratory scales but explores scales and epochs reachable only with large-scale galaxy surveys.
        Speaker: Laura Taddei (ITP Heidelberg, Germany)
      • 12:56
        Scaling in a network of cosmic necklaces 1m
        Speaker: David Weir (University of Stavanger, Norway)
    • 14:00 15:40
      CMB, LSS and cosmological parameters: CMB + LSS Main Hall ()

      Main Hall

      Convener: Ruth Durrer
      • 14:00
        CMB Lensing and Scale Dependent New Physics 20m
        Cosmic microwave background lensing has become a new cosmological probe, carrying rich information on the matter power spectrum and distances over the redshift range z≈1-4. We investigate the role of scale dependent new physics, such as from modified gravity, neutrino mass, and cold (low sound speed) dark energy, and its signature on CMB lensing. The distinction between different scale dependences, and the different redshift dependent weighting of the matter power spectrum entering into CMB lensing and other power spectra, imply that CMB lensing can probe simultaneously a diverse range of physics. We highlight the role of arcminute resolution polarization experiments for distinguishing between physical effects.
        Speaker: Eric Linder (UC Berkeley, United States)
      • 14:20
        On soft limits of large-scale structure correlation functions 20m
        We study soft limits of correlation functions for the density and velocity fields in the theory of structure formation. First, we re-derive the (resummed) consistency conditions at unequal times using the eikonal approximation. These are solely based on symmetry arguments and are therefore universal. Then, we explore the existence of equal-time relations in the soft limit which, on the other hand, depend on the interplay between soft and hard modes. We scrutinize two approaches in the literature: the time-flow formalism, and a background method where the soft mode is absorbed into a locally curved cosmology. The latter has been recently used to set up (angular averaged) ‘equal-time consistency relations’. We explicitly demonstrate that the time-flow relations and ‘equal-time consistency conditions’ are only fulfilled at the linear level, and fail at next-to-leading order for an Einstein de- Sitter universe. While applied to the velocities both proposals break down beyond leading order, we find that the ‘equal-time consistency conditions’ quantitatively approximates the perturbative results for the density contrast. Thus, we generalize the background method to properly incorporate the effect of curvature in the density and velocity fluctuations on short scales, and discuss the reasons behind this discrepancy. We conclude with a few comments on practical implementations and future directions.
        Speaker: Laura Sagunski (DESY, Germany)
      • 14:40
        Intensity Mapping and One-Point Statistics 20m
        Intensity mapping is a promising new technique for studying the large-scale structure of the universe at redshifts inaccessible to traditional galaxy surveys. Intensity mapping studies typically focus on two-point statistics of a map such as the power spectrum. However, because these maps are highly non-Gaussian, there is a wealth of additional information which can be obtained by studying the one-point statistics. We illustrate this using a simple model of an intensity mapping survey targeting CO at redshift 3. Using a P(D) analysis, we demonstrate how to calculate the one-point PDF of a map from a galaxy luminosity function. We also study the effects of emission lines from foreground galaxies by considering a population of HCN emitting galaxies at redshift 2, and show that the one-point statistics can be used to recover information about the target CO population without resorting to cross-correlation studies. We then demonstrate how this one-point analysis can be used to break degeneracies present in the two-point statistics of an intensity map to obtain useful cosmological information.
        Speaker: Patrick Breysse (Johns Hopkins University, United States)
      • 15:00
        Measuring the speed of light with Baryon Acoustic Oscillations 20m
        We describe a new method to use Baryon Acoustic Oscillations to derive a constraint on the possible variation of the speed of light. The method relies on the fact that there is a simple relation between the angular diameter distance maximum and the Hubble function evaluated at the same maximum-condition redshift, which includes speed of light c. We evaluate if current or future missions can be sensitive enough to detect any variation of c.
        Speaker: Vincenzo Salzano (University of Szczecin, Poland)
      • 15:20
        Non-parametric Reconstruction of the Hubble Expansion History 20m
        Non-parametric reconstruction is useful for constraining quantities that are potentially varying with time. A common practice is to replace the continuous function with an interpolation over a set of points or bins. This approach often involves many degrees of freedom, so that the constraints become too weak to be informative. In this presentation, we discuss priors that can help reduce the uncertainties of reconstructed Hubble parameters and dark energy equation of state. Specifically, we propose a physically motivated prior that requires the Hubble expansion rate to be a non-decreasing function of redshift. Tests using SDSS-III and SNLS supernova data show significant improvement with such a prior, and the reconstructed Hubble parameters are consistent with measurements from ages of passively evolving galaxies.
        Speaker: Hu Zhan (National Astronomical Observatories of China, China)
    • 14:00 15:40
      Dark Energy: DE Rm 115+116 ()

      Rm 115+116

      Convener: Dragan Huterer
      • 14:00
        Cosmology of massive gravity 20m
        The quest for a stable, compelling, cosmology of massive gravity. I will introduce some of the everyday tools of massive (bi)gravity and then illustrate the latest developements. Particular attention will be devoted to the so-called generalized massive gravity model, its observational viability as well as its stability as a qft.
        Speaker: Matteo Fasiello (Stanford University, United States)
      • 14:20
        UV inspired f(R) 20m
        Motivated by UV realisations of Starobinsky-like inflation models, we study generic exponential plateau-like potentials to understand whether an exact $f(R)$-formulation may still be obtained when the asymptotic shift-symmetry of the potential is broken for larger field values. Potentials which break the shift symmetry with rising exponentials at large field values only allow for corresponding $f(R)$-descriptions with a leading order term $R^{n}$ with $1 < n < 2$, regardless of whether the duality is exact or approximate. The $R^2$-term survives as part of a series expansion of the function $f(R)$ and thus cannot maintain a plateau for all field values. We further find a lean and instructive way to obtain a function $f(R)$ describing $m^2\phi^2$-inflation which breaks the shift symmetry with a monomial, and corresponds to effectively logarithmic corrections to an $R+R^2$ model. These examples emphasise that higher order terms in $f(R)$-theory may not be neglected if they are present at all. Additionally, we relate the function $f(R)$ corresponding to chaotic inflation to a more general Jordan frame set-up. In addition, we consider $f(R)$-duals of two given UV examples, both from supergravity and string theory. Finally, we outline the CMB phenomenology of these models which show effects of power suppression at low-$\ell$.
        Speaker: Benedict Broy (Theory Group, DESY, Germany)
      • 14:40
        Modified gravity inside astrophysical bodies 20m
        Many theories of modified gravity, including the well studied Horndeski models, are characterized by a screening mechanism that ensures that standard gravity is recovered near astrophysical bodies. In a recently introduced class of gravitational theories that goes beyond Horndeski, it has been found that new derivative interactions lead to a partial breaking of the Vainshtein screening mechanism inside any gravitational source, although not outside. We study the impact of this new type of deviation from standard gravity on the structure of astrophysical bodies.
        Speaker: Ryo Saito (Laboratoire APC, France)
      • 15:00
        Numerical forecasts for atom interferometry experiments constraining modified gravity 20m
        Current acceleration of the cosmic expansion leads to co%u010Fncidence as well as fine-tuning issues in the framework of general relativity. Dynamical scalar field have been introduced in response of these problems, some of them invoking screening mechanisms for passing local tests of gravity. Recent lab experiments based on atom interferometry in a vacuum chamber have been proposed for testing modified gravity models. So far only analytical computations have been used to provide forecasts. We derive numerical solutions for chameleon models that take into account the effect of the vacuum chamber wall in relation with its size. With this realistic distribution of the chameleon field in the chamber, we refine the forecasts that were derived with analytical computations. We highlight specific effects due to the vacuum chamber that are potentially interesting for future experiments and extend our results to additional models like the symmetron.
        Speaker: Sandrine Schloegel (UNamur, Belgium)
      • 15:20
        Equation of state of dark energy in f(R) gravity 20m
        f(R) gravity is one of the simplest generalizations of general relativity, which may explain the accelerated cosmic expansion without introducing a cosmological constant. Transformed into the Einstein frame, a new scalar degree of freedom appears and it couples with matter fields. In order for f(R) theories to pass the local tests of general relativity, it has been known that the chameleon mechanism with a so-called thin-shell solution must operate. If the thin-shell constraint is applied to a cosmological situation, it has been claimed that the equation-of-state parameter of dark energy w must be extremely close to -1. We argue this is due to the incorrect use of the Poisson equation which is valid only in the static case. By solving the correct Klein-Gordon equation perturbatively, we show that a thin-shell solution exists even if w deviates appreciably from -1
        Speaker: Kazufumi Takahashi (RESCEU The University of Tokyo, Japan)
    • 14:00 15:40
      Dark Matter: DM Rm 207 ()

      Rm 207

      Convener: Ki-Young Choi
      • 14:00
        Detecting Particle Dark Matter Signatures by Cross-Correlating Gamma-Ray Anisotropies with Weak Lensing 20m
        Both gravitational lensing and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe. Indeed DM structures are responsible for the bending of light due to the gravitational lensing effect, and those same objects can emit gamma rays, either because they host astrophysical sources or directly by particle DM annihilations/decays. Such gamma rays should therefore exhibit strong correlation with the gravitational lensing signal, correlation that can provide novel information on the composition of the extragalactic gamma-ray background (EGB). Here, I show that if the DM contribution to the EGB is significant enough, although compatible with current observational bounds, its strong correlation with gravitational lensing makes such signal potentially detectable by combining forthcoming gamma-ray and weak-lensing experiments. Moreover, I present results on the first evidence of the cross-correlation between gamma-ray data provided by the Fermi Large Area Telescope and lensing of the cosmic microwave background as measured by the Planck satellite.
        Speaker: Stefano Camera (Jodrell Bank Centre for Astrophysics, United Kingdom)
      • 14:20
        Interplay of ID, DD, and LHC searches in the MSSM 20m
        We investigate the prospects for detection of neutralino dark matter in the 19-parameter phenomenological MSSM (pMSSM). We explore very wide ranges of the pMSSM parameters but pay particular attention to the higgsino-like neutralino at the 1 TeV scale, which has been shown to be a well motivated solution in many constrained supersymmetric models, as well as to a wino-dominated solution with the mass in the range of 2-3 TeV. We consider the present bounds on the parameter space from direct and indirect detection experiments and we focus on prospects for detection of the Cherenkov Telescope Array (CTA). We find that, with 500 hours of observation, CTA will provide a highly sensitive way of searching for dark matter that will be partially overlapping and partially complementary with 1-tonne detector and collider searches, thus being instrumental to effectively explore the nearly full parameter space of the pMSSM.
        Speaker: Enrico Maria Sessolo (National Centre for Nuclear Research, Poland)
      • 14:40
        Explaining the Galactic Center Excess with the MSSM 20m
        The Fermi/LAT experiment measures a spherically symmetric excess in gamma-ray flux from the Galactic Center. The gamma-ray excess could be explained by annihilating dark matter. We aim to explain the Galactic Center Excess (GCE) via a neutralino in resonance with the higgs pseudoscalar. The MSSM parameter spaced is scanned in order to find the best fit to the gamma-ray flux signal measured at Fermi/LAT, while also maintaining the right relic abundance, higgs mass, higgs -> W W decay rate, and current direct detection constraints. In the mA - tan \beta plane, we do a \chi^2 analysis and show the best fit regions. Next LHC run will be able to probe part of the most promising parameter space.
        Speaker: Alejandro Lopez (University of Michigan, United States)
      • 15:00
        The relic density of heavy neutralinos 20m
        We will discuss the relic density of TeV-scale neutralino dark matter in the pMSSM. We have recently developed a framework enabling us to calculate the Sommerfeld enhanced relic density in general pMSSM scenarios. We will present the results of a thorough investigation of certain regions of parameter space, focussing in particular on departures from the well known pure wino scenario: namely the effect of sfermion masses being non-decoupled and of allowing non-negligible higgsino or bino components in the lightest neutralino. The results reveal a number of phenomenologically interesting but so far unexplored regions of parameter space. Near the region where the Sommerfeld enhancement is resonant, the combined effect of non-decoupled sfermions and significant higgsino-wino mixing allows regions with both the correct relic density and the potential for sizeable indirect detection rates.
        Speaker: Andrzej Hryczuk (TU Munich, Germany)
      • 15:20
        Nano-explosive detector for Dark Matter and Neutrinos 20m
        Speaker: Maciej Gorski (National Centre for Nuclear Research, Poland)
    • 14:00 15:40
      Inflation and phase transitions: Inflation + PT Rm 111+112

      Rm 111+112

      Convener: Kari Enqvist
      • 14:00
        Dynamically Induced Planck Scale and Inflation 20m
        Theories where the Planck scale is dynamically generated from dimensionless interactions provide predictive inflationary potentials and super-Planckian field variations. We first study the minimal single-field realisation in the low-energy effective field theory limit, finding the predictions $n_s \approx 0.96$ for the spectral index and $r \approx 0.13$ for the tensor-to-scalar ratio, which can be reduced down to $\approx 0.04$ in presence of large couplings. Next we consider agravity as a dimensionless quantum gravity theory finding a multi-field inflation that converges towards an attractor trajectory that predicts $n_s \approx 0.96$ and $0.003 $<$ r $<$ 0.13$, interpolating between the quadratic and Starobinsky inflation. These theories relate the smallness of the weak scale to the smallness of inflationary perturbations: both arise naturally because of small couplings, implying a reheating temperature of $10^{7-9}$ GeV. A measurement of $r$ by Keck/Bicep3 would give us information on quantum gravity in the dimensionless scenario.
        Speaker: Antonio Racioppi (NICPB, Estonia)
      • 14:20
        Composite Cosmology 20m
        I will discuss the appeal of pseudo-Goldstone bosons (pGBs) for the generation of scales in Early Universe cosmology. In particular, I will demonstrate how a pGB inflaton can solve the hierarchy problem of inflation (the tension between the Lyth bound and the inflationary scale as preferred by CMB anisotropies), while avoiding the problems with trans-Planckian scales that are typically associated with related models. The same mechanism can give rise to the dynamical generation of the electroweak scale through a composite Higgs, thus also addressing the EW hierarchy problem. I will discuss both inflation and reheating in this setup, and show how it naturally connects to both EW physics and a UV completion.
        Speaker: Djuna Croon (University of Sussex, United Kingdom)
      • 14:40
        Tensor and scalar perturbations from dilaton-induced gauge fields 20m
        We study the primordial scalar and tensor perturbations in inflation scenario involving a spectator dilaton in addition to the conventional inflaton field. In our setup, the rolling dilaton causes a tachyonic instability of gauge fields, leading to a copious production of gauge fields in the superhorizon regime, which generates additional scalar and tensor perturbations through gravitational interactions. Our major concern is the possibility to enhance the tensor to scalar ratio "r" relative to the standard result from vacuum fluctuations, while satisfying the observational constraints. For such possibility, the dilaton field is allowed to be stabilized before the end of inflation, but after the CMB scales exit the horizon. We show that for the inflaton slow roll parameter "epsilon" > 10^-3, the tensor to scalar ratio in our setup can be enhanced only by a factor of O(1) compared to the standard result. However, for smaller epsilon, a much larger enhancement can be achieved, so that our setup can give rise to r > 0.01 even when epsilon << 10^-3. The tensor perturbation sourced by the spectator dilaton can have a strong scale dependence, and is generically red-tilted.
        Speaker: Kiwoon Choi (KAIST, Republic of Korea)
      • 15:00
        Is it Inflation? 20m
        Recent data from the Cosmic Microwave Background and Large-Scale structure confirm the basic predictions of inflation in the early universe: a Gaussian, adiabatic spectrum of density perturbations with correlations on super-Hubble length scales. Furthermore, the density perturbations are known to be nearly (but not exactly) scale-invariant over a factor of at least a thousand in wavelength. I ask the question: what is the most general conclusion that can be drawn from these observational facts about the universe, consistent with standard General Relativity? Are superhorizon scalar modes a "smoking gun" for inflation, or are other scenarios possible? What would an observation of primordial tensor modes add?
        Speaker: Will Kinney (SUNY Buffalo, United States)
      • 15:20
        Inflationary fossils in large scale structures 20m
        In some early universe scenarios, a correlation between a long-wavelength tensor perturbation with two short wavelength scalar-fluctuations may generate an observable signal in form of a quadrupolar power asymmetry. Alternatively, it may produce an off-diagonal contribution to the matter power spectrum which would represent a possible probe for primordial gravitational waves. We discuss how such intriguing possibilities come about in specific inflationary models.
        Speaker: Emanuela Dimastrogiovanni (ASU, United States)
    • 15:40 16:10
      Coffee 30m
    • 16:10 18:10
      CMB, LSS and cosmological parameters: CMB + LSS Main Hall ()

      Main Hall

      Convener: Bronisław Rudak
      • 16:10
        The SPIDER experiment: Instrument review, flight performance, and preliminary results 20m
        SPIDER is a balloon-borne experiment designed to image the polarization of the cosmic microwave background with the aim of constraining models of the early universe. The experiment performed successfully during a 17 day flight in the 2014-2015 Antarctic season. During this first flight, SPIDER deployed a total of 2000 detectors, operating at 94 and 150 GHz, to map approximately 10% of the sky in the Southern Galactic Hemisphere. The dataset generated during this first flight should help provide the electromagnetic, spatial, and angular constraints required to characterize the B-mode signal properties. We will briefly review the instrument design, discuss flight performance, and describe early analysis results. We will conclude with plans for a subsequent flight of the SPIDER payload.
        Speaker: Jon Gudmundsson (Stockholm University, Sweden)
      • 16:30
        Oscillations in the CMB bispectrum 20m
        Oscillating signatures in the correlation functions of the primordial density perturbations are predicted by a variety of inflationary models. A theoretical mechanism that has attracted much attention is a periodic shift symmetry as implemented in axion monodromy inflation. This symmetry leads to resonance non-gaussianities, whose key feature are logarithmically stretched oscillations. Oscillations are also a generic consequence of excited states during inflation and of sharp features in the potential. Oscillating shapes are therefore a very interesting experimental target. After giving an overview of these motivations, I will discuss how to search for these signatures in the CMB. Fast oscillations are difficult to search for with traditional estimation techniques, and I will demonstrate how targeted expansions, that exploit the symmetry properties of the shapes, allow to circumvent these difficulties. As a member of the Planck collaboration, I will discuss the Planck results that have been obtained using these methods in the bispectrum, as well as a joint search using bispectrum and power spectrum. Due to their low overlap with other non-gaussian shapes, oscillating bispectrum shapes are not exhaustively constrained and a potential discovery is therefore not yet ruled out. My talk will be based in particular on arxiv:1412.3461, arxiv:1505.05882 and Planck publications on inflation and non-gaussianities.
        Speaker: Moritz Munchmeyer (Universite Pierre et Marie Curie, Institute Astrophysique de Paris, France)
      • 16:50
        CMB bispectrum 20m
        Cosmic Microwave Background (CMB) is known as a remnant of Big-Bang, and lots of past works in cosmology have paid attention to its potential to prove the very early Universe. In these days, our main interests moved to quite fine structures of the Universe, for instance, the statistical properties of the primordial fluctuations constructing the large-scale structure, and in fact we can investigate them thanks to rapid and sophisticated development of observational technologies. The simplest way to quantify the non-trivial statistical properties of the fluctuations is to calculate their bispectrum, or three-point correlation function. In our previous work, we developed a novel formalism, curve-of-sight formula, to compute the bispectrum of CMB temperature fluctuations in JCAP 10 (2014) 051, and have been developing a new Boltzmann solver implementing the curve-of-sight formula. In this talk, we show the up-to-date numerical results of the CMB bispectrum using the curve-of-sight formula, and also report the current status of the development of our numerical code aiming at solving the 2nd-order Boltzmann equations.
        Speaker: Takashi Hiramatsu (Kyoto University, Japan)
      • 17:10
        Theoretical Predictions of Large Scale Clustering in the Lyman-alpha Forest 20m
        With the recent progress of Lyman-alpha forest power spectrum measurements, understanding of the bias between the measured flux and the underlying matter power spectrum is becoming crucial to the percent level cosmological interpretation of these measurements. Previous theoretical studies of this bias have used N-body and hydro-PM simulations and inferred large-scale bias parameters that are in reasonable agreement with observations. In this work we attempt to develop a deeper understanding of the physical origin of the large-scale biasing of the forest. We have run a series of hydrodynamic N-body simulations in order to compare numerically measured bias factors with analytical predictions from formulae derived by Seljak (2012) using second-order perturbation theory. We demonstrate the success of this theory in a fluctuating Gunn-Peterson approximation (FGPA) framework for certain regimes, and characterise its limitations due to hydrodynamic effects, such as thermal broadening, with the hope of improving future theoretical models. Deeper understanding of the large-scale Lyman-alpha biasing will help us in using the large-scale clustering of the forest as a cosmological probe beyond baryon acoustic oscillations.
        Speaker: Agnieska Cieplak (Brookhaven National Laboratory, United States)
      • 17:30
        On Planck Asymmetries, Alignments and Calibration. 20m
        I review several possible Anomalies for the Planck CMB data: the hemispherical power asymmetry, dipolar modulation and quadrupole-octupole alignments. I show that they are significantly affected by our proper motion. I also point out that the latter issue might be relevant also for the Calibration of the HFI instrument itself.
        Speaker: Alessio Notari (Universitat de Barcelona, Spain)
      • 17:50
        The effect of clustering dark energy on cosmological parameter estimation 20m
        Clustering dark energy presents interesting phenomonology in comparison to standard homogeneous dark energy models. We investigate the impact of clustering dark energy on structure formation. Employing the spherical collapse formalism we obtain the collapse and virial density thresholds, as well as additional mass contributions due to non-linear dark energy perturbations. For an accurate description, the halo mass function is carefully recalibrated to include these non-linear effects of clustering dark energy. Using our MCMC likelihood analysis of X-ray cluster samples calibrated with weak gravitational lensing data together with standard cosmological data sets, we constrain cosmological parameters when incorporating these non-linear corrections. We emphasise the impact on the constraints of the cosmological parameters and the relevance of including these corrections in the cluster mass function calculation.
        Speaker: Caroline Heneka (Dark Cosmology Centre, Denmark)
    • 16:10 18:10
      Dark Energy: DE Rm 115+116 ()

      Rm 115+116

      Convener: Dragan Huterer
      • 16:10
        Bimetric gravity is cosmologically viable 20m
        Bimetric theory describes gravitational interactions in the presence of an extra spin-2 field. It allows for many different types of cosmological solutions but not all of them are theoretically allowed, most of them are generically plagued by instabilities. We discuss the conditions of the absence of these ghost- and gradient instabilities and present a ghost-free model in which the gradient instabilities can be pushed back to unobservably early times. In this limit, the theory approaches general relativity with a technically-natural effective cosmological constant which is, remarkably, determined by the spin-2 interaction scale.
        Speaker: Frank Koennig (Institut fuer Theoretische Physik -Uni Heidelberg, Germany)
      • 16:30
        Tensor Modes in Bigravity: Primordial to Present 20m
        Massive bigravity, a theoretically consistent modification of general relativity with an additional dynamical rank two tensor, successfully describes the observed accelerated expansion of the Universe without a cosmological constant. Previous analyses of perturbations around a cosmological background have revealed power law instabilities in both the scalar and tensor sectors, leading to tremendous growth in the amplitude of perturbations. The amount of growth is strongly dependent on various parameters of the theory and the initial conditions, motivating an analysis of the initial conditions, evolution, and cosmological observables to determine the viability of these theories. Here we focus on the tensor sector. We compute observables, namely the tensor contribution to the temperature anisotropies in the Cosmic Microwave Background and the present-day stochastic gravitational wave background. Finding that our results depend heavily on the initial conditions, we analyze the primordial tensor perturbations generated in an inflationary cosmology. Despite the extreme growth of perturbations, we find that inflation generically yields initial conditions that, when evolved, give rise to a stochastic background observationally indistinguishable from standard General Relativity.
        Speaker: Alexandra Terrana (York University, Canada)
      • 16:50
        Consistent metric combinations in cosmology of massive bigravity 20m
        Massive bigravity models are interesting alternatives to standard cosmology. In most cases however these models have been studied for a simplified scenario in which both metrics take homogeneous and isotropic forms (Friedmann-Lemaitre-Robertson-Walker; FLRW) with the same spatial curvatures.The interest to consider more general geometries arises in particular in view of the difficulty so far encountered in building stable cosmological solutions with homogeneous and isotropic metrics. Here we consider a number of cases in which the two metrics take more general forms, namely FLRW with different spatial curvatures, Lemaitre, Lemaitre-Tolman-Bondi (LTB), and Bianchi I, as well as cases where only one metric is linearly perturbed. We discuss possible consistent combinations and find that only some special cases of FLRW–Lemaitre, LTB–LTB and FLRW–Bianchi I combinations give consistent, non-trivial solutions.
        Speaker: Henrik Nersisyan (Heidelberg University ITP, Germany)
      • 17:10
        Mapping dark energy with fundamental couplings 20m
        We recently extended Principal Component Analysis based methods to constrain the dark energy equation of state (originally developed for Type Ia supernovae and other low redshift probes) to spectroscopic tests of the stability of fundamental couplings, which can probe higher redshifts. In this talk I will use these methods to quantify the gains in sensitivity obtained by combining spectroscopic measurements expected from ESPRESSO at the VLT and the high-resolution ultra-stable spectrograph for the E-ELT (known as ELT-HIRES) with future supernova surveys. I will also discuss the dark energy impact of supernovas beyond the acceleration phase (i.e., deep in the matter era), and show how the dark universe may be mapped as deep as redshift 4.
        Speaker: Ana Caterina Leite (Centro de Astrofísica da Universidade do Porto, Portugal)
      • 17:30
        The Effective Field Theory approach to dark energy and modified gravity phenomenology 20m
        I will discuss the relevance of the Effective Field Theory (EFT) approach in testing modified gravity and dark energy models that aim at solving the problem of cosmic acceleration. In particular I will review the EFT construction and its implementation into the Einstein-Boltzmann solver EFTCAMB that is a powerful and versatile tool that can be used for several objectives. It can be employed to evolve the full dynamics of linear perturbations in any given single field dark energy or modified gravity model, once the latter is mapped into the EFT formalism. It offers a numerical implementation of EFT as a model-independent framework to test gravity on cosmological scales. It has a built-in check for the fulfilment of general stability conditions such as the absence of ghost and superluminal propagation of perturbations and handles phantom-divide crossing models. It does not rely on any quasi-static approximation but rather evolves the full dynamics of perturbations on all linear scales which is an important feature in view of the accuracy and scale range of upcoming surveys. At last I will present some of the observational results obtained with this code and discuss its latest developments toward testing gravity with large scale structure data.
        Speaker: Marco Raveri (SISSA, Italy)
      • 17:50
        Perturbations of Cosmological and Black hole Solution in Bi-gravity 20m
        We investigate perturbations of a class of time-dependent spherically symmetric solutions in bi-gravity, which includes both FLRW space time and Schwarzschild de Sitter space time. We consider the solutions which can be obtained only when the parameters of bi-gravity satisfy a special relation. In this case, It is known that the equation of motion for spherically symmetric space time reduces to the Einstein equation with an effective cosmological constant. We find this property is true even in the level of general perturbation, namely, the equations of motion of perturbations become the perturbed Einstein equation. This result shows, even if any observation about the perturbation of spherically symmetric space time coincide with the prediction of General Relativity, we can not dissmiss the theoy of bi-gravity.
        Speaker: Daisuke Yoshida (Tokyo Institute of Technology, Japan)
    • 16:10 18:10
      Dark Matter: DM Rm 207 ()

      Rm 207

      Convener: Ki-Young Choi
      • 16:10
        The Warmness of Dark Matter from the Lyman alpha forest 20m
        We reconsider the problem of determining the warmness of dark matter from the Lyman-alpha forest. In particular, we have re-analyzed the previous work of Viel et al 2013, based on high resolution Lyman-alpha forest spectra. We allow different cosmic thermal history than the one considered in the previous work; these cosmic thermal history are in agreement with other theoretical and observational constraints at higher redshift. We obtain new constraints on the warm dark matter (WDM) mass, mWDM >= 2.13 keV at 2-sigma level. We conclude that, due to astrophysical uncertainties, the likelihood function considered in Viel et al cannot improve the constraints on WDM mass with respect to previous constraints from SDSS.
        Speaker: Antonella Garzilli (Leiden University, Netherlands)
      • 16:30
        Minimal Asymmetric Dark Matter 20m
        n the early Universe, any particle carrying a conserved quantum number and in chemical equilibrium with the thermal bath will unavoidably inherit a particle-antiparticle asymmetry. A new particle of this type, if stable, would represent a candidate for asymmetric dark matter (DM) with an asymmetry directly related to the baryon asymmetry. We study this possibility for a minimal DM sector constituted by just one (generic) $SU(2)_L$ multiplet $\chi$ carrying hypercharge, assuming that at temperatures above the electroweak phase transition an effective operator enforces chemical equilibrium between $\chi$ and the Higgs boson. We argue that limits from DM direct detection searches severely constrain this scenario, leaving as the only possibilities scalar or fermion multiplets with hypercharge $y = 1$, preferentially in large $SU(2)$ representations, and with a mass in the few TeV range. (Based on arXiv:1503.01119) arXiv:1503.01119 arXiv:1503.01119arXiv:1503.01119 arXiv:1503.01119
        Speaker: Martin Krauss (INFN - Laboratori Nazionali di Frascati, Italy)
      • 17:10
        Dark-Matter Bound States from Feynman Diagrams 20m
        If dark matter couples directly to a light force mediator, then it may form bound states in the early universe and in the non-relativistic environment of haloes today. In this talk I will present a field-theoretic framework for the computation of bound-state formation cross-sections, de-excitation and decay rates, in theories with long-range interactions. At low relative velocities of the interacting particles, the formation of bound states is enhanced by the Sommerfeld effect. For scalar particle-antiparticle pairs, we show that bound-state formation can be faster than annihilation into radiation in the regime where the Sommerfeld effect is important.
        Speaker: Marieke Postma (Nikhef, Netherlands)
      • 17:30
        A search for dark matter annihilation in the newly discovered dwarf galaxy Reticulum 2 20m
        I will present results from a search for gamma-ray emission in nine Milky Way satellites recently discovered in the Dark Energy Survey. The nearest of these, Reticulum 2, shows evidence for a signal in public Fermi data. The detected emission is consistent with annihilating dark matter with a particle mass less than a few hundred GeV. Different ways of treating the background yield different significances -- ranging from 2.3 sigma to greater than 3.7 sigma (after trials) -- and I will discuss the caveats involved. Spectroscopic observations of member stars are used to infer the density profile of Reticulum 2, showing that its annihilation signal should be among the largest of the known dwarfs. Finally, I will discuss tests that a dark matter interpretation must pass.
        Speaker: Savvas Koushiappas (Brown University, United States)
      • 17:50
        Cosmological black holes and accretion: causal structure and models for the dark sector 20m
        The generalized McVittie solution, representing a central time-dependent mass in an expanding cosmological background, has been shown to be an exact solution of a self-gravitating subset of the Horndeski class of scalar field actions, and constitutes an important example of an analytic solution for hairy black holes. Following the analysis performed on its fixed-mass counterpart, we demonstrate that a time-dependent central mass may have a significant impact on the overall causal structure of the spacetime. The metric always has an event horizon at future cosmological time infinity in the appropriate limits, but the character of the horizon depends on the accretion and cosmological histories in the bulk. The possible limits are a black-hole horizon, a pair of black- and white-hole horizons separated by a bifurcating 2-sphere, or an entirely white-hole horizon. The last case is only possible if there is accretion onto the central mass.
        Speaker: Daniel Guariento (Perimeter Institute for Theoretical Physics, Canada)
    • 16:10 18:10
      Inflation and phase transitions: Inflation + PT Rm 111+112 ()

      Rm 111+112

      Convener: Kari Enqvist
      • 16:10
        CP-violating top-Higgs coupling and electroweak phase transition 20m
        Given the limited precision on the measurement of the Higgs self-coupling and the top Yukawa coupling, we explore the possibility for anomalous Higgs couplings within the nonlinear realisation of the electroweak symmetry, together with a CP-violating top-Higgs sector. In such a scenario, the electroweak phase transition may be strongly first order and the additional sources of CP-violation may lead to successful electroweak baryogenesis.
        Speaker: Jason Tsz Shing Yue (University of Sydney, Australia)
      • 16:30
        Correlation Functions in Stochastic Inflation 20m
        In stochastic inflation, the quantum effects on the dynamics of the long wavelength perturbations are modelled by a stochastic noise. To study quantum corrections to inflationary observables, one thus needs to extract correlation functions of cosmological perturbations from this formalism. I will show how this can be done in practice, for all order correlation functions, in a non perturbative and fully analytical way. In the classical limit, when the potential is not too flat, quantum corrections are Planck suppressed and the standard results are recovered. In particular, this is the case for the modes within the CMB observable window. For some inflationary potentials however, quantum modifications can become large on smaller and/or larger scales, and we discuss the physical consequences of this effect.
        Speaker: Vincent Vennin (ICG, University of Portsmouth, United Kingdom)
      • 16:50
        Shaft Inflation 20m
        A new family of inflation models is introduced and studied. The models are characterised by a scalar potential which, far from the origin, approximates an inflationary plateau, while near the origin becomes monomial, as in chaotic inflation. The models can be obtained in the context of global supersymmetry starting with a superpotential, which interpolates from a generalised monomial to an O'Raifearteagh form for small to large values of the inflaton field respectively. It is demonstrated that the observables obtained, such as the scalar spectral index and the tensor to scalar ratio, are in excellent agreement with the latest observations. Some discussion of initial conditions and eternal inflation may be included.
        Speaker: Konstantinos DIMOPOULOS (Lancaster University, United Kingdom)
      • 17:10
        The squeezed limit of the bispectrum for multifield inflation 20m
        Soft limits of correlation functions of the primordial curvature perturbation provide a unique opportunity to confront theoretically clean results against observations of non-Gaussianity. In this work we calculate the squeezed limit of the bispectrum of the curvature perturbation produced by multifield inflation, which allows for a very large hierarchy of scales. This is achieved by taking different exit times for different modes, as required in the squeezed limit. We allow the field perturbations to evolve between these exit times and then apply the delta-N formalism from the time the last mode exits to find the bispectrum and other observables in the squeezed limit. This allows one to investigate the highly squeezed limit, and we find significant differences to previous results which were valid only for a mild squeezing. This work was produced in collaboration with David Mulryne, and will appear on the arxiv shortly.
        Speaker: Zachary Kenton (Queen Mary University of London, United Kingdom)
      • 17:30
        How does canonical quantum gravity affect scalar and tensor perturbations during inflation? 20m
        We calculate corrections originating from canonical quantum gravity to the power spectra of gauge-invariant scalar and tensor perturbations during inflation. This is done by performing a semiclassical Born–Oppenheimer type of approximation to the Wheeler–DeWitt equation, from which we obtain a Schrödinger equation with a quantum-gravitational correction term. We perform our calculation both for a de Sitter universe as well as for a generic slow-roll model. The quantum-gravitational correction term leads to a modification of the power spectra on the largest scales, which is too small to be measurable, and we find a correction to the tensor-to-scalar ratio at the second order in the slow-roll parameters. We also compare these findings with results that were obtained in this context using just scalar-field perturbations in a non-gauge-invariant way.
        Speaker: Manuel Krämer (Institute of Physics, University of Szczecin, Poland)
      • 17:50
        Warm intermediate inflation in the Randall–Sundrum II model in light of Planck 2015 and BICEP2 results. 20m
        In the present work we study the possibility that a higher dimensional scenario, in particular the RS II brane-world model, can describe the dynamics of the Universe in its very early epochs. We propose this possibility in the context of warm inflation scenario, for a Universe evolving according to the intermediate scale factor, and how a generalized form of the dissipative coefficient $\Gamma(T,\phi)\propto T^{m}/\phi^{m-1}$ influences the dynamics of our model. We study the inflationary dynamics in the weak and strong dissipative regimes of warm inflation, under the slow-roll approximation, and find solutions to the full effective Friedmann equations in the brane-world framework. By other hand, we will compute the cosmological perturbations, which are written in terms of several parameters. In order to constrain these parameters, we consider the recent data from BICEP2 and Planck 2015, together with the necessary condition for warm inflation, $T>H$, and also the condition from the weak (or strong) dissipative regime.
        Speaker: Nelson Videla (Universidad de Chile, Chile)
    • 09:00 10:40
      CMB, LSS and cosmological parameters: CMB + LSS Main Hall ()

      Main Hall

      Convener: Tomasz Bulik
      • 09:00
        The Abundance of Extreme Cosmic Voids 20m
        Cosmic voids have been shown to be an effective probe of cosmology, complementary to galaxy clusters. But how reliable are the current theoretical models for void abundance? In this talk, I will explain how the theory of "extreme cosmic voids" can be used as a consistency test for theories of void abundance. I will give a simple derivation of the size of the largest voids expected within a given redshift and volume. This extreme-void model is based on the exact extreme-value statistics which has previously been successfully applied to massive galaxy clusters. I will show that, when compared with simulations and observations (e.g. SDSS voids), the Sheth and Van de Weygaert model (and simple adjustments thereof) generally yields a poor fit to the extreme-void abundance even though it appears to give a good fit to the void distribution over some radius range. I will discuss some insights into possible resolutions. Based on 1502.07705 (JCAP in press).
        Speaker: Siri Chongchitnan (University of Hull, United Kingdom)
      • 09:20
        Tension between the power spectrum of density perturbations measured on large and small scales 20m
        There is a tension between measurements of the amplitude of the power spectrum of density perturbations inferred using the Cosmic Microwave Background (CMB) and directly measured by Large-Scale Structure (LSS) on smaller scales. We show that this tension exists, and is robust, for a range of LSS indicators including clusters, lensing and redshift space distortions and using CMB data. One obvious way to try to reconcile this is the inclusion of a massive neutrino which could be either active or sterile. Using Planck and a combination of LSS data we find that (i) for an active neutrino the sum of the neutrinos is m=(0.357+-0.99) eV and (ii) for a sterile neutrino m_sterile= (0.67+-0.18) eV and N_eff= 0.32+-0.20. This is, however, at the expense of a degraded fit to Planck temperature data, and we quantify the residual tension at 2.5- and 1.6-sigma for massive and sterile neutrinos respectively. We also consider alternative explanations including a lower redshift for reionization that would be in conflict with polarisation measurements made by WMAP and ad-hoc modications to primordial power spectrum.
        Speaker: Tom Charnock (University of Nottingham, United Kingdom)
      • 09:40
        Intrinsic galaxy size correlations and their importance for weak lensing 20m
        We present a simple model for describing intrinsic correlations for galaxy sizes based on the halo model. Studying these correlations is important both to improve our understanding of galaxy properties and because it is an important potential systematic for weak lensing size magnification measurements. Our model assumes that the density field drives these intrinsic correlations and we also model the distribution of satellite galaxies. We calculate the possible contamination to measurements of lensing convergence power spectrum from galaxy sizes, and show that the cross-correlation of intrinsic sizes with convergence is potentially an important systematic. We also explore how these intrinsic size correlations may affect surveys with different redshift depth. We find that, in this simple approach, intrinsic size correlations cannot be neglected in order to estimate lensing convergence power spectrum for constraining cosmological parameters.
        Speaker: Robert Crittenden (Institute of Cosmology and Gravitation, United Kingdom)
      • 10:00
        CMB lensing and deflection angles in high precison cosmology 20m
        We present a new method to compute the deflection of light rays in a perturbed FLRW geometry. By using the properties of the Geodesic Light Cone (GLC) gauge where null rays propagate at constant angular coordinates irrespectively of the given (inhomogeneous and/or anisotropic) geometry, the gravitational deflection of null geodesics can then be obtained in any other gauge. This connection can be done by expressing the angular coordinates of the given gauge in terms of the GLC angular coordinates. We apply this method to the standard Poisson gauge, including scalar perturbations, and give the full result for the deflection effect in terms of the direction of observation and observed redshift up to second order, and up to third order for the leading lensing terms. Furthermore, we also discuss the connection with literature and estimate the effects of lensing on the CMB temperature.
        Speaker: Giuseppe Fanizza (Universita di Bari, Italy)
      • 10:20
        Is there evidence for anisotropy in CMB data? 20m
        Large scales in the Cosmic Microwave Background (CMB) may break statistical isotropy. Bianchi models are often invoked as a possible explanation for these low-\ell features: they provide an anisotropic underlying pattern over which the usual stochastic fluctuations are superimposed. However, the Bianchi models generally employed in the analysis of CMB data — despite mimicking the anomalies in the CMB temperature map — overproduce B-mode polarisation due to the very specific way in which they break isotropy. In this work, we consider a more physical class of Bianchi models that satisfy polarisation constraints and test for their signatures in Planck temperature and polarisation maps; WMAP data are also analysed for comparison. We take into account all the possible ways to break Friedmann-Robertson-Walker isotropy, whilst preserving homogeneity. We also test for the well-known Bianchi models that are more commonly employed in the literature, and show that we are able to improve constraints on these models by extending the likelihood to high \ell. Nested sampling techniques are employed to determine whether the Bayesian evidence favours anisotropic universes over the standard Lambda-CDM scenario.
        Speaker: Daniela Saadeh (University College London, United Kingdom)
    • 09:00 10:40
      Dark Energy: DE Rm 207 ()

      Rm 207

      Convener: Marek Biesiada
      • 09:00
        Numerical Problems in Perturbed Coupled Quintessence 20m
        In this talk I will outline our research into the evolution of perturbations in coupled quintessence with multiple fluids and scalar fields. I will explain what coupled quintessence is and why it is of interest and will introduce a new Python code developed by myself in conjunction with my collaborators. There are a vast number of different coupled quintessence models and potentials and we have developed a general code to allow the testing of any such potential - PYESSENCE. I will also present some initial results from this ongoing work and outline future work utilising this new code.
        Speaker: Alexander Leithes (Queen Mary University of London, United Kingdom)
      • 09:20
        Cosmology with strong gravitational lensing systems 20m
        In the era of massive galactic surveys, strong gravitational lensing systems have entered a stage in which we observe their growing significance in astrophysics and cosmology. In our work we present a catalog of 118 strong gravitational lensing systems built on SLACS, BELLS, LSD and SL2S samples and we use them to demonstrates that strong lensing data provide a good quality tool for constraining the values of cosmological parameters in dark energy equation of state. We focused ourselfes on two cosmological scenarios explaining observed present accelerating expansion of the Universe - XCDM cosmology where dark energy is represented by an unknown kind of fluid with barotropic equation of state in which: i) w parameter has a constant value and ii) w parameter is allowed to evolved with redshift according to CPL parametrization (w(z) = w0 + w1 * (z/(1+z))). In our work we assume two models of mass distribution in lensing galaxies: SIS model with isothermal profile and more general one with arbitrary power-law index g (allowing it also to evolve wth redshift g(z)). Our results are in agreement both with w and g values obtained by other authors and also shows a trend of being complementary to latest supernova Ia data.
        Speaker: Aleksandra Piorkowska (University of Silesia, Poland)
      • 09:40
        Interacting dark energy in light of CMB, lensing, and BAO data 20m
        This presentation will introduce the research [1] in which we employed the Planck CMB temperature anisotropy and lensing data, and baryon acoustic oscillation (BAO) data to constrain a phenomenological $w$CDM model, where dark matter and dark energy interact. We assumed time-dependent equation of state parameter for dark energy, and treated dark matter and dark energy as fluids whose energy-exchange rate is proportional to the dark-matter density. The CMB data alone leave a strong degeneracy between the interaction rate and the physical CDM density parameter today, $\omega_c$, allowing a large interaction rate $|\Gamma| \sim H_0$. However, the BAO data break this degeneracy. As a novelty we exploit the CMB lensing potential likelihood, which probes the matter perturbations at redshift $z\sim 2$ and is very sensitive to the growth of structure, and hence one of the tools for discerning between the $\Lambda$CDM model and its alternatives. In models with $w<-1$ the CMB and BAO data favour energy transfer from dark energy to dark matter at the rate of about 35\% of today's Hubble rate while the non-interacting model is 3$\sigma$ "disfavoured" by these data. Adding the CMB lensing data to the constraint budget, restores the non-interacting model to or near to the border of the 68\% CL region. References [1] J.Valiviita, E. Palmgren. arXiv:1504.02464. Accepted for publication in JCAP (2015).
        Speaker: Elina Palmgren (Helsinki institute of physics, Finland)
      • 10:00
        Dark energy:Testing gravity in Voids and Halos 20m
        Massive gravity can dynamically and transparently provide of the acceleration of the of the universe, where the mass of the graviton sets the energy scale of dark enregy. We find the parameter space of massive graivty which easily accomodates the observed acceleration of the Universe by SNa, and BAO with the most recent Planck data. The same parameter space also makes unique predictions for weak lensing signals for voids and halos for up coming Telescopes such as Euclid and LSST.
        Speaker: Douglas Spolyar (Stockholm University OKC, Sweden)
      • 10:20
        The Dynamical Evolution Of A Galaxy Cluster: The Local Effect Of Dark Energy 20m
        The role of Dark Energy (DE) in the long term evolution of galaxy clusters is the main topic of this talk. Recently, observational data of the outflow of galaxies in the Virgo cluster, suggest that DE can also act on a small cosmic scales, like a single galaxy cluster. By means of direct N-body simulations and taking advantage of the latest generation of computational hardware and software, we performed several simulations in which a galaxy cluster is undergo to the action of the DE force and the gravitational one induced by the gas. With our work we reproduced the so called Hubble diagram, with the aim to highlight the outflow of the galaxies lying in the outermost region of the cluster. By comparing the different simulations, our preliminary results suggest that the observed outflow of galaxies is likely due to the local effect of DE, which instead weakly affects, as expected, the inner regions of the cluster. Furthermore the precision of the N-body method used, allows us to follow the merging process among some galaxies with the aim to reproduce the formation of a single compact object in the centre of the cluster.
        Speaker: Martina Donnari (Sapienza University of Rome, Italy)
    • 09:00 10:40
      Inflation and phase transitions: Inflation Rm 111+112 ()

      Rm 111+112

      Convener: Kari Enqvist
      • 09:00
        Mixed Inflaton and Spectator Field Models: CMB constraints and \\mu distortion 20m
        We consider a model where primordial density fluctuations are generated both from the inflaton and the spectator field such as the curvaton. In general, the power spectra generated from different scalar fields exhibit a different scale dependence, thus it is possible that fluctuations sourced by one field dominates on large scales, while those from the other field can give a significant contribution on small scales. Current observations of CMB can measure the fluctuations on large scales very precisely, however, those on much smaller scales can also be probed in the future, one of which is the CMB mu distortion. We first discuss the current constraint on the mixed source model from observations of CMB and LSS. Then, given the constraint, we study the CMB mu distortion in the model and discuss the prospects of how we can probe such a mixed model by using future observations of the mu distortion.
        Speaker: Tomo Takahashi (Saga University, Japan)
      • 09:20
        L-R neutrino oscillation during preheating 20m
        When the Higgs field starts oscillation after Higgs inflation, gauge bosons will be produced non-perturbatively near the Enhanced Symmetry Point (ESP). Just after the particle production, when the Higgs field is going away from the ESP, gauge bosons gain mass and decay or annihilate into Standard Model (SM) fermions. In that way, left-handed neutrinos can be generated from the heavy gauge bosons. If one assumes see-saw mechanism, the mass matrix of a pair of left and right-handed neutrinos is non-diagonal. Although their mixing in the mass eigenstates is negligible in the true vacuum, it could be significant near the edge of the Higgs oscillation. Therefore, if the gauge bosons are transferred into left-handed neutrinos near the edge, there will be ``neutrino oscillation'' between the left and the right-handed neutrinos. Leptogenesis from this mechanism is briefly examined. If the idea is applied to mu-MSSM, the initial condition for the Hot Big Bang is totally different.
        Speaker: Tomohiro Matsuda (Saitama Institute of Technology, Japan)
      • 09:40
        Stabilizing the Planck mass shortly after inflation 20m
        In this talk, I will present recent work focusing on a model of inflation embedded in a scalar-tensor theory. This model contains two fields, one that drives inflation, and a second that stabilizes the Planck mass (or the gravitational constant) in the early universe. In this model, the stabilization occurs a few efolds after inflation. We show, by performing a numerical calculation, that the non-minimal coupling of the second field to the Ricci scalar can boost the amplitude of the curvature perturbation, even if the Planck mass varies only a small amount.
        Speaker: Adam Christopherson (University of Florida, United States)
      • 10:00
        Single superfield inflation, moduli stabilization, and supersymmetry breaking 20m
        Supergravity is a well-motivated framework to study inflation. Recently (large field) inflation in supergravity with a single inflaton superfield (thus without the stabilizer field) obtained interests and was developed. Two major approaches are those of (1) Ketov and Terada (2014), and (2) Roest and Scalisi (2015), and also Linde (2015). We study consequences of combining these models of single superfield inflation with moduli and supersymmetry (SUSY) breaking sectors. In the simplest case, the inflaton superpotential is that of Polonyi model, and the scales of inflation, SUSY breaking, and moduli stabilization (a la KKLT) are the same. This turns out to be a severe constraint on the model. We also explore other models of this kind and derive constraints on inflationary models.
        Speaker: Takahiro TERADA (The University of Tokyo, Japan)
      • 10:20
        Massive primordial black holes from hybrid inflation as dark matter and the seeds of galaxies 20m
        A scenario where massive Primordial Black Holes (PBH) are produced from the collapse of large curvature perturbations generated during a mild waterfall phase of hybrid inflation will be presented. I will give the values of the inflaton potential parameters leading to a PBH mass spectrum producing abundances comparable to those of Dark Matter today, while the matter power spectrum on scales probed by CMB anisotropies agrees with Planck data. These PBH could have acquired large stellar masses today, via merging, and the model passes both the constraints from CMB distortions and micro-lensing. This scenario is supported by Chandra observations of numerous BH candidates in the central region of Andromeda. Moreover, the tail of the PBH mass distribution could be responsible for the seeds of supermassive black holes at the center of galaxies, as well as for ultra-luminous X-rays sources. The considered effective hybrid potential can originate e.g. from D-term inflation with a Fayet-Iliopoulos term of the order of the Planck scale but sub-planckian values of the inflaton field.
        Speaker: Sebastien clesse (University of Namur, Belgium)
    • 09:00 10:40
      Inflation and phase transitions: PT Rm 115+116 ()

      Rm 115+116

      Convener: Mark Hindmarsh
      • 09:00
        Domain wall formation via axion roulette and axion domain wall baryogenesis 20m
        We point out that domain wall formation is a more common phenomenon in the Axiverse than previously thought. Level crossing could take place if there is a mixing between axions, and if some of the axions acquire a non-zero mass through non-perturbative effects as the corresponding gauge interactions become strong. The axion potential changes significantly during the level crossing, which affects the axion dynamics in various ways. We find that, if there is a mild hierarchy in the decay constants, the axion starts to run along the valley of the potential, passing through many crests and troughs, until it gets trapped in one of the minima; the "axion roulette". The axion dynamics exhibits a chaotic behavior during the oscillations, and which minimum the axion is finally stabilized is highly sensitive to the initial misalignment angle. Therefore, the axion roulette is considered to be accompanied by domain wall formation. We also propose a new scenario of baryogenesis, in which annihilation of axion domain walls generates a sizable baryon asymmetry. In particular, it is consistent with high-scale inflation which generates a large tensor-to-scalar ratio within the reach of future CMB B-mode experiments. The gravitational waves produced by the domain wall annihilation and its implications for the future gravitational wave experiments are also discussed.
        Speaker: Naoya Kitajima (Tohoku University, Japan)
      • 09:20
        Chasing monopoles 20m
        Our ongoing calibration of the analytical models for Semilocal strings using field theory simulations indicate that the velocities of the string ends will be of great significance. It is known that Semilocal string ends behave as global monopoles, so we are developing a technique to measure global monopole velocities using field theory simulations. In this presentation, we will explain the technique we propose to measure these velocities. Finally we will give some results and we will use them to calibrate the analytical models for global monopoles.
        Speaker: Asier Lopez-Eiguren (University of the Basque Country, Spain)
      • 09:40
        Random walks in deSitter 20m
        We show how the full quantum description of a scalar field with quartic self-interaction in de Sitter spacetime is equivalent to Brownian motion of a particle in a medium of de Sitter temperature T_DS = H/2π on large wavelengths. We then argue that the system exhibits a fluctuation-dissipation relation and its equilibrium distribution is Maxwell-Boltzmann, implying kinetic and potential energies of comparable magnitudes. The stochastic kinetic energy of the field causes de Sitter spacetime to cool down slowly with a corresponding decrease of the effective vacuum energy. The transition to equilibrium is a semiclassical process beyond the scope of perturbation theory for interacting fields.
        Speaker: Gerasimos Rigopoulos (Newcastle University, United Kingdom)
      • 10:00
        The observational position of simple non-minimally coupled inflationary scenarios 20m
        Recently, there has been a large amount of work considering theories of inflation which lead to a common observational prediction - the Universal Attractors. I will present the attractor structure in the case of the strong, non-minimal coupling to gravity variety of these models, identifying a shift of the attractor from the expected Starobinsky point and determining conditions for approach to the attractor. The observational position of these models will then be assessed with particular emphasis on the restraints future observations of primordial B-modes may be able to place on the non-minimal coupling to gravity. Finally, after the departure from the original prediction in the case of the single field model I will present some ideas on a multi-field extension, showing that the current simple interpretation of how the fields move through field space during inflation does not appear to be all that is required in explaining the phenomenology of such models.
        Speaker: David Edwards (Institute for Astronomy, University of Edinburgh, United Kingdom)
      • 10:20
        Astrophysical and Cosmological Probes of Cosmic String Networks 20m
        The discovery of a cosmic string network would provide compelling evidence for a symmetry-breaking phase transition in the early universe, and thereby further our understanding of particle physics at high energies with implications for baryogenesis, magnetogenesis, inflation, and string theory. Whereas high tension string networks, such as those associated with a GUT-scale phase transition, have characteristic gravitational signatures like lensing, these gravitational observables become ineffectual at probing a lighter string network, which could be associated with the EW- or SUSY-breaking phase transition. In this regime, we can still seek out the string network via the particle radiation that it emits. In this talk, I will review the perturbative particle emission mechanism and present our particle radiation "catalog" that summarizes the spectra for various different radiation channels. Then I will discuss the implications for detectability through different astrophysical (cosmic ray) and cosmological (BBN/CMB) probes.
        Speaker: Andrew Long (KICP, United States)
    • 10:40 11:10
      Coffee 30m
    • 11:10 12:50
      CMB, LSS and cosmological parameters: CMB Main Hall ()

      Main Hall

      Convener: Tomasz Bulik
      • 11:10
        New approach to cosmological perturbation theory from an effective action 20m
        The large scale structure of the Universe will become the leading observational probe in cosmology in the near future. However, the proper analysis of structure formation at small scales requires non-linear effects to be taken into account. Straightforward attempts to do so within perturbation theory faced several problems such as the appearance of non-physical infra-red (IR) enhancements from soft modes at each given loop correction. These spurious IR - enhancements, although cancelled out upon summing over all loop corrections, complicate tremendously the analysis of physical IR - effects at higher loop order. In my talk I will propose a new method to account for the non-linear clustering of dark matter. This method is based on the ideas of effective action, path integral and RG flow. I will show that our approach is free of spurious IR - enhancements and makes possible to resumm the physical effects of long-wavelength perturbations that are crucial for the BAO peaks. I will compare our IR - resummation method to the other known techniques and test it against N-body data for the power-spectrum and the correlation function.
        Speaker: Mikhail Ivanov (Ecole Polytechnique Federale de Lausanne, Switzerland)
      • 11:30
        Anisotropic Correlations in Fourier Phases 20m
        Correlations in Fourier phases of the cosmological density field arise as a consequence of non-linear structure formation. Since two-point statistics are blind to phase factors, measures of pure phase information will not only be independent of the conventional power spectrum or two-point function, they also do not suffer from Gaussian variance on the modulus of the density field and linear bias. They may thus be regarded as an additional and potentially valuable probe of large-scale structure in upcoming galaxy surveys. Starting from a recently proposed measure of phase information, the line correlation function, I will present an anisotropic generalisation that is capable of detecting anisotropies in the distribution of galaxies. Based on a number of numerical studies, I will then discuss how the Alcock-Paczynski effect and kinematical redshift-space distortions can in principle be measured from Fourier phases.
        Speaker: Alexander Eggemeier (University of Sussex, United Kingdom)
      • 11:50
        Backreaction in Growing Neutrino Quintessence 20m
        In Growing Neutrino Quintessence strong backreaction effects, induced from large neutrino non-linearities, alter the cosmic history. I will present results obtained from N-body simulations which includes relativistic particles, non-linear scalar field equations and backreaction effects. Including the backreaction effects a realistic cosmology is hard to realize. This points to the need of models with field dependent couplings. In those models the neutrino perturbations are still large, but the backreaction effects are much smaller, a realistic cosmology is possible.
        Speaker: Florian Fuehrer (Institut fuer Theoretische Physik, Germany)
      • 12:10
        Evading non-linearities: Baryon Acoustic Oscillations at the linear point 20m
        Cosmology has made fundamental progress thanks to the role of standard rulers. The acoustic peak in the Large Scale Structure clustering correlation function is one of them. However, in the era of precision cosmology, its power has been highly challenged by how late time non-linearities distort the correlation function. Fortunately this is not the end of the story! I will explain how we can evade non-linearities identifying a scale in the correlation function, called the “linear point”, that is an excellent cosmological standard ruler: its position is insensitive to non-linear gravity, redshift space distortions, and scale-dependent bias at the 0.5% level; it is geometrical, i.e. independent of the power spectrum of the primordial density fluctuation parameters. Moreover, the linear point increases its appeal as it is easily identified irrespectively of how non-linearities distort the correlation function. Equally relevant, the correlation function amplitude at the linear point is similarly insensitive to non-linear corrections to within a few percent. Therefore, exploiting the particular Baryon features in the correlation function, we propose three new estimators for growth measurements. We perform a preliminary test in current data finding encouraging results and motivating more careful future investigations.
        Speaker: Stefano Anselmi (Case Western Reserve University, United States)
      • 12:30
        . 20m
    • 11:10 12:50
      CMB, LSS and cosmological parameters: LSS Rm 207 ()

      Rm 207

      Convener: Marek Biesiada
      • 11:10
        General relativistic corrections in N-body simulations -- The N-body gauge 20m
        We discuss different gauge choices and their advantages in the context of N-body simulations. The initial conditions for N-body simulations are usually generated by employing the Zel'dovich approximation. We show that the initial displacements generated in this way generally receive a first-order relativistic correction. We identify a novel gauge, called N-body gauge in the following, in which this relativistic correction is absent. Therefore the Zel'dovich approximation provides accurate initial conditions in the N-body gauge. Furthermore we show that a conventional Newtonian N-body simulation includes all first-order relativistic contributions in the absence of pressure perturbations and anisotropic stresses if we identify the coordinates in Newtonian simulations with those in the N-body gauge. We therefore conclude that the N-body gauge is uniquely suited for N-body simulations. When setting the initial conditions using the Zel'dovich approximation and running a conventional Newtonian N-body simulation the results include all linear relativistic effects if the output is understood in terms of the N-body gauge. In addition we analyse the limitations of the N-body gauge due to pressure perturbations and anisotropic stresses from residual radiation or a non standart cosmology.
        Speaker: Christian Fidler (CP3 , Belgium)
      • 11:30
        Weak lensing signals induced from second-order vector perturbation 20m
        The standard cosmological perturbation theory is well established by by a number of observations such as the CMB anisotropy or the Large scales structure. The standard cosmological perturbation theory includes three independent modes, i.e., scalar, vector, and tensor modes. The scalar mode is the dominant component in our Universe and has been well determined by cosmological observations. Conversely, the vector mode is neglected in the standard first-order cosmological perturbation theory since it only has a decaying mode. This situation changes if the cosmological perturbation theory is expanded up to second order. The second-order vector and tensor modes are inevitably induced by the product of the first-order scalar modes. We study the effect of the second-order vector mode on the weak lensing curl- and B-modes.
        Speaker: Shohei Saga (Nagoya University, Japan)
      • 11:50
        Using dark energy to suppress power at small scales 20m
        There remains a slight but chronic tension between the latest Planck results and low-redshift observables: power seems to be consistently lacking at late times. I will describe how a simple model of dark energy, which has the same expansion history as LCDM, induces a scale-dependent correction to the growth rate of dark matter, suppressing power small scales. Since observations in the late universe are performed at smaller scales, this brings the early and late universe into better agreement. I will argue that such scale-dependent behaviour is completely generic in models of dynamical dark energy and modified gravity and must be properly accounted for in modelling of theories and observations.
        Speaker: Ignacy Sawicki (University of Geneva, Switzerland)
      • 12:10
        Constraining higher-order primordial non-Gaussianity from power spectra and bispectra of imaging survey 20m
        Detection of primordial non-Gaussianity (PNG) is recognized as a powerful probe of cosmic inflation, and it can give an important clue for the generation mechanism of primordial density fluctuations. In this talk, we specifically consider the local-type PNG and discuss how well one can tightly constrain the higher-order non-Gaussianity parameters (gNL and tauNL) as well as the leading order (fNL). While the recent CMB measurement by Planck puts a tight constraint on fNL, the constraints on gNL and tauNL are still weak. It is however known that the local-type PNG induces a strong scale-dependent behavior in the galaxy/halo clustering, and this can provide a way to put a more stringent constraint on PNG. Here, we examine the statistical power of this effect by combining both power spectra and bispectra of photometric/imaging galaxy surveys. Fisher matrix analysis reveals that the combination of power spectra and bispectra can break the degeneracy between non-Gaussianity parameters (fNL,gNL and tauNL) and this will give simultaneous constraints on those three parameters. As a result, upcoming surveys like the Large Synoptic Survey Telescope have the potential to improve the constraints on PNG much tighter than those obtained from the CMB measurements, giving us an opportunity to test the single-field consistency relation, tauNL>=(36/25)fNL2.
        Speaker: Ichihiko Hashimoto (Kyoto University, Japan)
      • 12:30
        How to model the effect of small-scale structures on light propagation? 20m
        In standard cosmology, observations are interpreted as if light propagated through a universe whose inhomogeneities are modeled by perturbations with respect to the FLRW spacetime. However, the very narrow light beams associated with point-like sources—such as supernovae—probe the Universe at extremely small scales (~AU), up to which the perturbative approach should break down. In this talk, I will present an alternative framework where the lensing due to small-scale structures is treated as a diffusion process.
        Speaker: Pierre Fleury (IAP, France)
    • 11:10 12:50
      Inflation and phase transitions: Inflation Rm 111+112 ()

      Rm 111+112

      Convener: Kari Enqvist
      • 11:10
        Liberating vector fields from their CMB anisotropy constraint 20m
        The contribution of cosmological vector fields to the CMB is strongly constrained by the bound on the anisotropy parameter g, allowing a direction-dependent contribution only to a puny 0.2% level, thus establishing the global isotropy of the CMB to high precission. In this talk I present a scenario whereby a vector field, produced during inflation and free from ghost and perturbative instabilities, avoids this anisotropy constraint by imposing an observable direction-dependent perturbation on relatively small patches of the CMB only. I describe the scale-dependent statistical distribution of the curvature pertubation contributed by the vector field and discuss the naturalness of the setting and its implications.
        Speaker: Juan Carlos Bueno Sanchez (Universidad Antonio Narino, Colombia)
      • 11:30
        Renormalization in Higgs inflation 20m
        We study the renormalization of theories with large non-minimal scalar-gravity coupling, of which Higgs inflation (inflation with the Higgs field playing the role of the inflaton) is the most prominent example. Despite the popularity of these models, their renormalization has never been worked out systematically. We provide an on-shell renormalization scheme, organized as an expansion in inverse powers of the non-minimal coupling constant. Our toy model is a complex, non-minimally coupled U(1) scalar field coupled to a fermion and a gauge field. We compute its relevant betafunctions, comment on their validity, show the generalization to the full theory of Standard Model Higgs inflation and compare these results with the approximate ones encountered in the literature.
        Speaker: Sander Mooij (FCFM, Universidad de Chile, Chile)
      • 11:50
        Inflation, quantum gravity and the latest Planck data 20m
        In this talk, I will discuss about one of the most sucesfull inflationary models according to the latest Planck data, namely the Starobinskys model. I will focus on the significance of quantum corrections in this context, and how this model could be understood as part of a more fundamental framework.
        Speaker: Ippocratis Saltas (University of Lisbon, Portugal)
      • 12:10
        A universal threat to single-field inflation 20m
        The simplest single-field models of inflation are sufficient to explain the cosmological data. However, inflation is an ultraviolet-sensitive phenomenon, and embedding inflation into high-energy physics requires taking into account the possible effects on inflation of heavy scalar fields. Model-builders usually assume or construct potentials such that they are stabilized by a potential well. Here, we uncover a simple and universal geometrical mechanism by which these heavy fields can get destabilized. This can modify the properties or ruin otherwise successful single-field inflationary models. We illustrate this mechanism by several explicit examples.
        Speaker: Sebastien Renaux-Petel (IAP, France)
      • 12:30
        Non-metric inflation 20m
        A generalisation of the Weyl geometry, where the non-metricity and torsion are given by a single vector field, is presented. Taking into account the leading (quadratic) curvature correction in this geometry results in a one-parameter extension of the Starobinsky inflation, the so-called alpha-attractor model.
        Speaker: Tomi Koivisto (Nordita, Sweden)
    • 11:10 12:50
      Inflation and phase transitions: PT Rm 115+116 ()

      Rm 115+116

      Convener: Mark Hindmarsh
      • 11:10
        Three-Dimensional Quantum Bubble Collisions 20m
        First-order phase transitions proceed through the nucleation and subsequent collision of bubbles. In false vacuum eternal inflation, such collision events are ubiquitous and provide a possible avenue to observationally test the multiverse. They also play an important role in early high temperature phase transitions. I will present results for the full three-dimensional nonlinear dynamics of pairwise bubble collisions, including for the first time the effects of (initially small) quantum fluctuations. This significantly extends the standard treatment of these collisions, where the field profile is assumed to possess a spatial SO(2,1) symmetry and the dynamics reduces to one spatial dimension. However, quantum fluctuations are present and break the assumed symmetry, although the breaking may initially be very small. I will show that accounting for the dynamics of these fluctuations leads to a dramatic breakdown of the SO(2,1) symmetry in a wide class of potentials. Initially, the fluctuations experience a linear parametric instability, which can be interpreted as an inhomogeneous version of Bogoliubov particle production. At the onset of mode-mode coupling, the bubble walls in the collision region dissolve, leaving behind a population of localized oscillating blobs of field known as oscillons. This has implications for the production of gravitational waves and black holes in bubble collisions.
        Speaker: Jonathan Braden (University College London, United Kingdom)
      • 11:30
        Fate of the Primordial Higgs Condensate 20m
        If the Higgs potential remains close to the Standard Model prediction the light Higgs field gets locally displaced from vacuum during inflation. Observational ramifications of the primordial Higgs condensate crucially depend on its subsequent evolution. We discuss the relaxation of the condensate using analytical methods and numerical lattice computations. The dominant decay channel is the resonant production of weak gauge bosons where non-Abelian interactions play a crucial role. Unlike in the Abelian case, they quickly extend the momentum distribution towards high values, efficiently destroying the condensate after the onset of backreaction. For inflation at the scale $H = 10^{8}$ GeV, we find that $90$\% of the Higgs condensate has decayed after $n\sim 7$ oscillation cycles. This differs significantly from the Abelian case where, given the same couplings strengths, most of the condensate would persist after the resonance.
        Speaker: Sami Nurmi (University of Jyvaskyla, Finland)
      • 11:50
        Bounds on the hidden Universe 20m
        Although detecting primordial non-Gaussianity (NG) would provide an incredibly rich window onto the interaction physics of the inflaton, one might wonder what we could conclude about its nature if all we end up observing is consistent with adiabatic, Gaussian and scale invariant initial conditions. In this talk we highlight how in principle, one can still infer a great deal. Fields that are completely decoupled from the inflaton still interact with gravitational strength interactions, and although these interactions are very suppressed at low energies, a large number of them can consistently imprint interesting signatures on cosmological observables. If one were to assume nothing other than adiabaticity in the early universe, we discuss how one can use the absence of primordial NG to place bounds on the hidden field content of the universe. These bounds become more and more meaningful the more stringent the observational bounds become. We discuss the implications for various string theoretic and supersymmetric phenomenological scenarios and prospects from future observations.
        Speaker: Subodh Patil (University of Geneva, Switzerland)
      • 12:10
        Gravitational Waves in the Supersymmetric Extensions of the SM 20m
        In many extensions of the Standard Model of particle physics (SM) the LHC experimental data impose a stringent bound on the strength of the electroweak phase transition and, in turn, on the stochastic gravitational waves background that this transition can produce. In this talk we consider a simple supersymmetric extension of the SM and we identify a parameter region where the electroweak phase transition is close to metastability. We discuss the collider phenomenology and gravitational wave signals of this region. It results that in this model a sizeable stochastic gravitational wave background is possible without violating the present LHC constraints. The prospective detection of such a gravitational wave signal is presented.
        Speaker: Germano Nardini (DESY, Germany)
      • 12:30
        Vector and tensor contributions to the curvature perturbation at second order 20m
        We derive the evolution equation for the second order part of the curvature perturbation using standard techniques of cosmological perturbation theory. The result is valid at all scales and includes all contributions from vector and tensor perturbations, as well as anisotropic stress. We write all our results purely in terms of gauge invariant quantities, so as to facilitate future work in any choice of gauge. Taking the large-scale approximation, we find that a conserved quantity exists only if, in addition to the non-adiabatic pressure, the transverse traceless part of the anisotropic stress tensor is also negligible.
        Speaker: Pedro Gregorio Carrilho (Queen Mary University of London, United Kingdom)
    • 12:50 14:00
      Lunch 1h 10m
    • 14:00 17:30
      Excursion 3h 30m
    • 19:30 22:00
      Banquet 2h 30m

      Villa Foksal

    • 09:00 10:10
      Plenary Main Hall ()

      Main Hall

      Convener: Ruth Gregory
      • 09:00
        Theoretical approaches to the Dark Energy paradigm 35m
        Speaker: David Polarski (University Montpellier, France)
      • 09:35
        Quantum break time for cosmological constant 35m
        Speaker: Gia Dvali (Ludwig-Maximilians-Universitaet Muenchen, Germany)
    • 10:10 10:40
      Coffee 30m
    • 10:40 12:30
      Plenary Main Hall ()

      Main Hall

      Convener: Fernando Quevedo
      • 10:40
        Aligned Axionic Inflation 35m
        Speaker: Hans-Peter Nilles (University of Bonn, Germany)
      • 11:15
        Cosmological Collider Physics 35m
        Speaker: Juan Maldacena (IAS, United States)
      • 11:50
        Area Law and Second Law in Cosmology 35m
        Speaker: Raphael Bousso (UC Berkeley, United States)
    • 12:30 14:00
      Lunch 1h 30m
    • 14:00 15:40
      CMB, LSS and cosmological parameters: CMB + LSS Main Hall ()

      Main Hall

      Convener: Marek Demiański
      • 14:00
        Cosmology on the Largest Scales 20m
        Ultra-large cosmic scales supply a wealth of information most valuable for strengthening our knowledge of the Universe. For instance, they can teach us about the physical processes at play during the inflationary epoch, or enable us to either further confirm or rule out Einstein's theory of general relativity. This is because: on the one hand, there are relativistic corrections to the Newtonian prediction that only become important on extremely large scales; and, on the other hand, those scales may hide signatures of modifications to gravity. However, the largest cosmic scales have hitherto proven to be utterly difficult to access. Here, I show how it will be possible to access the ultra-large scale information with the next generation of cosmological surveys such as Euclid or the Square Kilometre Array. I will also show that ultra-large scale effects must be properly taken into account in the view of future cosmological experiments, if we do not want to bias our results.
        Speaker: Stefano Camera (Jodrell Bank Centre for Astrophysics, United Kingdom)
      • 14:20
        How much useful cosmological information can we capture beyond the linear regime of structure formation? 20m
        During the nonlinear evolution from Gaussian initial conditions, Fourier modes of the cosmological matter density field gradually develop statistical dependence. A precise understanding of this cosmic (co)variance is essential for the ultimate success of the ambitious upcoming wide-field surveys targeting cosmic acceleration or modified theories of gravity. I will discuss the dynamics of the information within the dark matter field and how its affects the power spectrum, and implications for cosmological parameter inference. I’ll show how to design from first principles simple yet efficient analysis of the matter field, that eventually must rely on a non-linear transformation of the field. These transformations such as the logarithmic transformation and its generalization the A* transformation are typically much better tracers of the linear density and recover up to a factor of a few more information.
        Speaker: Julien Carron (University of Sussex, United Kingdom)
      • 14:40
        Decaying Dark Matter and the Discrepancy in sigma_8 20m
        We consider decaying dark matter (DDM) as a resolution to the possible tension between cosmic microwave background (CMB) and weak lensing (WL) based determinations of the amplitude of matter fluctuations, $\sigma_8$. We perform N-body simulations in a model where dark matter decays into dark radiation and develop an accurate fitting formula for the non-linear matter power spectrum, which enables us to test the DDM model by the combined measurements of CMB, WL and the baryon acoustic oscillation (BAO). We employ a Markov chain Monte Carlo analysis to examine the overlap of posterior distributions of the cosmological parameters, comparing CMB alone with WL+BAO. We find an overlap that is significantly larger in the DDM model than in the standard CDM model. This may be hinting at DDM, although current data is not constraining enough to unambiguously favour a non-zero dark matter decay rate $\Gamma$. From the combined CMB+WL data, we obtain a lower bound $\Gamma^{-1}>97$ Gyr at 95 % C.L, which is less tight than the constraint from CMB alone.
        Speaker: Toyokazu Sekiguchi (University of Helsinki, Finland)
      • 15:00
        An introduction to 21cm cosmology using HI intensity mapping 20m
        21cm cosmology is a new and exciting area of research with a great deal of potential. We have now entered an era of precision cosmology, but almost all of the information used to achieve this precision has come from the CMB at redshift z ~ 1100 or from galaxy surveys below z ~ 1.5. Using observations of the redshifted 21 cm line of atomic hydrogen (HI) we can look at previously unexplored epochs, like the Dark Ages and the Epoch of Reionization (EoR), as well as complement (and compete with) the results from galaxy surveys at low redshifts. In this talk I will present recent work on Weak Lensing studies using 21-cm radiation from the EoR as well as from a post-reionization "intermediate" redshift range (2
        Speaker: Alkistis Pourtsidou (University of Portsmouth, United Kingdom)
      • 15:20
        Robust forecasts on inflationary science from the foreground-obscured, gravitationally lensed CMB polarisation 20m
        Recent results from the BICEP2, Keck Array and Planck collaborations demonstrate that Galactic foregrounds are an unavoidable obstacle in the search for evidence of inflationary gravitational waves in the cosmic microwave background (CMB) polarisation. Beyond the foregrounds, the effects of lensing by intervening large-scale structure further obscure all but the strongest inflationary signals permitted by current data. With a plethora of ongoing and upcoming experiments aiming to measure these signatures, careful and self-consistent consideration of experiments’ foreground- and lensing-removal capabilities is critical in obtaining credible forecasts of their performance. I will present a Python-based Fisher framework that performs just this task. Using data-driven foreground models with user-defined components, this tool first estimates the residuals and noise in the CMB maps produced by maximum-likelihood component separation. It then forecasts the ability of experiments to delens these maps, via iterative CMB-only techniques or cross-correlation with external data, and thence constrain inflationary cosmology. Publicly available through an online interface, this tool allows the next generation of CMB telescopes to foreground-proof their designs, optimise their frequency coverage to maximise scientific output, and determine where cross-experimental collaboration would be most beneficial.
        Speaker: Stephen Feeney (Imperial College London, United Kingdom)
    • 14:00 15:40
      Dark Energy: DE Rm 115+116 ()

      Rm 115+116

      Convener: Ruth Gregory
      • 14:00
        Structure formation in fast transition UDM models 20m
        Dark matter and dark energy are usually considered to be two separate components in the energy budget of the Universe. A simple extension to this hypothesis is to consider that they could be different aspects of a single component. This class of models is hence dubbed Unified Dark Matter (UDM) models. UDM models could cluster and hence give origin to cosmic structures if the adiabatic sound speed of the fluid is small enough, but this is achieved only with a severe fine-tuning of the parameters. A particularly interesting sub-class of UDM models solving this issue is characterised by a fast transition between a standard matter-like era and a late epoch with accelerated expansion (cosmological constant or dark energy). In addition these models can avoid the problems affecting the Chaplygin gas models. An important point lacking in literature is a rigorous analysis of structure formation in adiabatic fast transition models, clearly defining the equation of motions of the clustering part of the fluid. I will show results of structure formation in UDM fast transition models within the framework of the spherical collapse model and a comparison with the standard approach for LCDM and dark energy models.
        Speaker: Francesco Pace (University of Manchester, United Kingdom)
      • 14:20
        A magnified glance into the Dark Sector: Probing cosmological models with strong lensing in A1689 20m
        In this work we constrain four alternative models to explain the late cosmic acceleration in the Universe: Chevallier-Polarski-Linder, interacting dark energy, Ricci holographic dark energy, and modified polytropic Cardassian. To test these models, we use mainly several strong gravitational lensing images of background galaxies produced by the galaxy cluster Abell 1689. We compare the value added by this cosmological probe with the power of other complementary probes: SNIa, BAO, and CMB. We present preliminary results for each model using these data. Finally, the SL measurements in galaxy clusters is a promising and powerful technique to constrain cosmological parameters considering the lens modeling is reconstructed for each cosmological model. Furthermore, this kind of test would be able to improve the constraints if the SL data of other galaxy clusters are considered.
        Speaker: Juan Magana (Institute of Physics and Astronomy Universidad de Valparaiso, Chile)
      • 14:40
        Cosmology in delta Gravity: A Classical Analysis and Phenomenology 20m
        We present a model of the gravitational field based on two symmetric tensors, $g_{\mu \nu}$ and $\tilde{g}_{\mu \nu}$. Besides, we have a new matter field given by $\tilde{\phi}_I = \tilde{\delta} \phi_I$, where $\phi_I$ are the original matter fields. We call them $\tilde{\delta}$ matter fields. This model, called $\tilde{\delta}$ Gravity, has excellent properties at the quantum level. It lives at one loop only, the classical equations of motion of the original fields are preserved and it is a finite quantum theory in vacuum. We find that massive particles do not follow geodesics, while trajectories of massless particles are null geodesics of an effective metric. We analyze some cases to study the effect of the new gravitational field. Firstly, we see the Schwarzschild case, where we get a modified deflection of the light produced by the sun. Secondly, we see the Non-Relativistic case, where we obtain the Post-Newtonian limit. We do a little analysis in the Newtonian limit to interpret $\tilde{\delta}$ matter like a dark matter contribution. Thirdly, we see the Cosmological case, where we get an accelerated expansion of the Universe without dark energy. A Big-Rip is necessary to explain the expansion. Additionally, we obtain a modified age of the universe and when the Big-Rip will happen. Finally, we introduce the effect of $\tilde{\delta}$ Gravity in inflation in a background level.
        Speaker: Pablo Gonzalez (Universidad de Chile, Chile)
      • 15:00
        Constraints on hybrid metric-Palatini models from background evolution 20m
        Two models of the hybrid metric-Palatini theory of gravitation are introduced. Their background evolution is explored, showing explicitly that one recovers standard General Relativity with an effective Cosmological Constant at late times. This happens because the Palatini Ricci scalar evolves towards and asymptotically settles at the minimum of its effective potential during cosmological evolution. We then use a combination of cosmic microwave background, Supernovae and baryonic accoustic oscillations background data to constrain the models' free parameters. For one model in particular, we are able to constrain the deviation from the gravitational constant G one can have at early times.
        Speaker: Vanessa Smer Barreto (University of Edinburgh, United Kingdom)
      • 15:20
        Brans –Dicke supergravity and the $\\Lambda$ naturalness problem 20m
        The successful $\Lambda CDM$ cosmological model requires a small but nonzero $\Lambda$ which appears to have an unnaturally small value compared to the supersymmetry breaking scale, typically $O(10^{-60}) m_{3/2}^4$ for $m_{3/2} \sim 10 TeV$. We explore the possibility of solving this naturalness problem in a special class of no-scale supergravity models which arise from a supersymmetric version of Brans-Dicke gravity, in which the Volkov and Brans-Dicke multiplets may be identified. These may be embedded in compactified string models, with the Brans-Dicke scalar given by the combination of dilaton and compactification breathing modes which leaves the 4 dimensional gauge couplings fixed. Assuming that 4 dimensional physics has an approximate symmetry under changes in this mode broken only by couplings between the low energy and gravitational or string sectors, the main one loop contribution to $\Lambda$ cancels between Brans-Dicke and gravitational (conformal compensator) F terms, and the leading contributions to $\Lambda$ now appear to be $O(m_{3/2}^8 m_{p}^{-4)}$, enabling a natural reconciliation between observational and particle physics estimates for $\Lambda$. The Brans-Dicke scalar has a range $O(m_{3/2}^{-1})$, lifting observational constraints on scalar gravity in this scenario.
        Speaker: Mike Hewitt (Canterbury Christ Church University, United Kingdom)
    • 14:00 15:40
      Dark Matter: DM Rm 207 ()

      Rm 207

      Convener: Kiwoon Choi
      • 14:00
        Inflationary Imprints on Dark Matter 20m
        A generic feature of Standard Model extensions with no drastic modifications to the Higgs potential is that the Higgs is a light and energetically subdominant field during inflation. Inflationary fluctuations generically displace the field from its vacuum generating a primordial Higgs condensate. This sets specific out-of-equilibrium initial conditions for the hot big bang epoch which could have significant observational ramifications. In this work we investigate how these initial conditions set by inflation affect the generation of dark matter in the class of portal scenarios where the Standard Model fields feel new physics only through Higgs mediated couplings. As representatives examples we will consider a scalar singlet s coupled to Higgs by V = λh2s2 and a singlet fermion N coupled to the scalar s by gsNN. This simple extension has interesting consequences as these singlets constitute a dark matter candidate originating from non-thermal production of scalar and fermion particles out from a singlet condensate and, moreover, reveals a novel connection between dark matter and fundamental inflationary physics.
        Speaker: Tommi Tenkanen (University of Helsinki, Finland)
      • 14:20
        Cogeneration and Pre-annihilation of Dark Matter by a New Gauge Interaction 20m
        Sphalerons of a new non-Standard Model gauge interaction can cogenerate dark matter and baryonic matter. They can also wipe out the symmetric component of the dark matter by a process of "pre-annihilation.
        Speaker: Stephen Barr (University of Delaware, United States)
      • 14:40
        Diluting the inflationary axion fluctuation by a stronger QCD in the early Universe 20m
        We propose a new mechanism to suppress the axion isocurvature perturbation, while producing the right amount of axion dark matter, within the framework of supersymmetric axion models with the axion scale induced by supersymmetry breaking. The mechanism involves an intermediate phase transition to generate the Higgs mu-parameter, before which the weak scale is comparable to the axion scale and the resulting stronger QCD yields an axion mass heavier than the Hubble scale over a certain period. Combined with that the Hubble-induced axion scale during the primordial inflation is well above the intermediate axion scale at present, the stronger QCD in the early Universe suppresses the axion fluctuation to be small enough even when the inflationary Hubble scale saturates the current upper bound, while generating an axion misalignment angle of order unity.
        Speaker: Sang Hui Im (Institute for Basic Science, Republic of Korea)
      • 15:00
        Generating Luminous and Dark Matter During Inflation 20m
        We propose a simple mechanism for generating ordinary luminous and dark matter during cosmic inflation. This scenario involves an extension of the Standard Model through the introduction of a dark matter candidate/s and an anomalous U(1)_X gauge group. The general framework developed is found to be able to replicate both the observed matter-antimatter asymmetry and the dark-to-visible matter mass density. (Based on arxiv: 1503.02366)
        Speaker: Neil Barrie (University of Sydney, Australia)
      • 15:20
        Dark matter with low reheating temperature 20m
        We revisit the calculation of the abundance of the supersymmetric dark matter particles: neutralino, gravitino, singlino and axino, taking into account the possibility that the reheating temperature of the Universe after inflation can be of the order of the electroweak scale or even lower. This leads to dramatic departures of predictions from the usually considered case of high reheating temperature. By means of Bayesian techniques, we study the regions of parameter spaces of respective models consistent with the LHC and low-energy data, in particular to check the prospects of direct detection in forthcoming experiments (neutralino) and to infer the impact of the constraints from successful nucleosynthesis and formation of large structures in the Universe (gravitino and axino).
        Speaker: Krzysztof Turzynski (University of Warsaw, Poland)
    • 14:00 15:40
      Inflation and phase transitions: Inflation + PT Rm 111+112 ()

      Rm 111+112

      Convener: Arttu Rajantie
      • 14:00
        Corpuscular Considerations on Cosmological Observables and Eternal Inflation 20m
        In my talk, I will first introduce the corpuscular framework, recently proposed by Gia Dvali and Cesar Gomez, in which space-time is described in terms of graviton Bose-Einstein condensates. Then I will present our recent quantitative investigations on this model regarding its cosmological implications, and will show how the cosmic microwave background power spectrum and the tensor-to-scalar ratio are affected. The last part of my talk reviews the paradigm of eternal inflation in the light of the corpuscular picture of space-time. Incorporating the inflaton fluctuations including quantum depletion (which is intrinsic to the graviton Bose-Einstein condensate description), I will show that the fraction of the space-time which has an increasing potential is always below the eternal-inflation threshold. This proves that for monomial potentials eternal inflaton is excluded. This is likely to hold for other inflation models as well.
        Speaker: Florian Kuhnel (The Oskar Klein Centre, Sweden)
      • 14:20
        Gauge and fermion preheating and the end of axion inflation 20m
        Axions are attractive candidates for theories of large-field inflation that are capable of generating observable primordial gravitational wave backgrounds. These fields enjoy shift-symmetries that protect their role as inflatons from being spoiled by coupling to unknown UV physics. This symmetry also restricts the couplings of these axions to other matter fields. At lowest order, the only allowed interactions are derivative couplings to gauge fields and fermions. These derivative couplings lead to the biased production of fermion and gauge-boson helicity states during and after inflation. I will describe some recent work on preheating in axion-inflation models that are derivatively coupled to Abelian gauge-fields and fermion axial-currents. For an axion coupled to U(1) gauge fields it is found –analytically and numerically- that preheating is efficient for a wide range of parameters. In certain cases the inflaton is seen to transfer all its energy to the gauge fields within a few oscillations. In most cases, three-dimensional lattice simulations showed that gauge fields on sub-horizon scales end preheating in an unpolarized state due to the existence of strong rescattering between the inflaton and gauge-field modes. Coupling an axion to Majorana fermions leads to biased production of fermion helicity-states which can have interesting phenomenological implications for leptogenesis.
        Speaker: Evangelos Sfakianakis (University of Illinois at Urbana-Champaign, United States)
      • 14:40
        Massive vector multiplet inflation with DBI type action 20m
        We investigate the inflation model with a massive vector multiplet in a case that the action of the vector multiplet is extended to the Dirac-Born-Infeld (DBI) type one in 4 dimensional N=1 supergravity. We show the massive DBI action, and find that the higher order corrections associated with the DBI-extension make the scalar potential flat with a simple choice of the matter couplings. We also discuss the DBI-extension of the new minimal Starobinsky model, and find that it is dual to a special class of the massive DBI action.
        Speaker: Yusuke Yamada (Waseda University, Japan)
      • 15:00
        Thermalization after Inflation 20m
        After inflation, inflaton converts its huge energy into radiation to create the hot Universe, which is referred to as reheating. Naively, one might guess that radiation produced via reheating soon attains the thermal distribution within the Hubble time. Under this instantaneous thermalization assumption, many attractive thermal mechanisms were proposed so far; such as thermal leptogenesis, thermal dark matter production, to name a few. In this talk, we examine this naive expectation, i.e. instantaneous thermalization, in the case of reheating via perturbative inflaton decay. We will show how the produced plasma becomes thermalized, and also discuss its implications on heavy particle production and symmetry restoration in the early Universe.
        Speaker: Kyohei Mukaida (Kavli IPMU, Japan)
      • 15:20
        Acoustically generated gravitational waves at a first order phase transition 20m
        We present large-scale numerical simulations of the gravitational radiation produced by a first order phase transition in the early universe. We show that the dominant source of gravitational waves is sound waves generated by the expanding bubbles of the low-temperature phase. The sound waves have a power spectrum with power-law form between scales set by the average bubble separation and the bubble wall width. In turn, the sound waves generate gravitational waves whose power spectrum also has a power-law form. These gravitational waves are generated at a rate proportional to the fluid length scale and the square of the fluid kinetic energy density. The general form of the gravitational wave power spectrum is different from that predicted by the envelope approximation, and the gravitational wave energy density is at least two orders of magnitude larger.
        Speaker: David Weir (University of Stavanger, Norway)
    • 15:40 16:10
      Coffee 30m
    • 16:10 18:10
      CMB, LSS and cosmological parameters: CMB + LSS Main Hall ()

      Main Hall

      Convener: Marek Demiański
      • 16:10
        Halo/Galaxy Bispectrum with Equilateral-type Primordial Trispectrum 20m
        We investigate the effect of equilateral-type primordial trispectrum on the halo/galaxy bispectrum. We consider three types of equilateral primordial trispectra which are generated by quartic operators naturally appearing in the effective field theory of inflation and can be characterized by three nonlinearity parameters, $g_{\rm NL} ^{\dot{\sigma}^4}$, $g_{\rm NL} ^{\dot{\sigma}^2 (\partial \sigma)^2}$, and $g_{\rm NL} ^{(\partial \sigma)^4}$. Recently, constraints on these parameters have been investigated from cosmic microwave background (CMB) observations by using WMAP9 data. In order to consider the halo/galaxy bispectrum with the equilateral-type primordial trispectra, we adopt the integrated perturbation theory (iPT) in which the effects of primordial non-Gaussianity are wholly encapsulated in the linear primordial polyspectrum for the evaluation of the biased polyspectrum. We show the shapes of the halo/galaxy bispectrum with the equilateral-type primordial trispectra, and find that one type of the primordial trispectrum provides the same scale dependence as the gravity-induced halo/galaxy bispectrum. On the other hand, the other two-types of primordial trispectra characterized by provide the common scale dependence which is different from that of the gravity-induced halo/galaxy bispectrum on large scales.
        Speaker: Shuntaro Mizuno (Waseda University, Japan)
      • 16:30
        Dark energy and non-linear power spectrum 20m
        We investigate the effects of homogeneous general dark energy on the non-linear matter perturbation in fully general relativistic context. The equation for the density contrast contains even at linear order new contributions which are non-zero for general dark energy. Taking into account the next-to-leading corrections, the total power spectrum with general dark energy deviates from the $\Lambda$CDM spectrum, which is nearly identical to that in the Einstein-de Sitter universe, as large as a few percent at scales comparable to that for the baryon acoustic oscillations and increases on smaller scales. The contribution from the curvature perturbation, which is absent in the Newtonian theory, exhibits even more drastic difference larger than 100%, while the amplitude is heavily suppressed on all scales.
        Speaker: Jinn-Ouk Gong (Asia Pacific Center for Theoretical Physics, Republic of Korea)
      • 16:50
        Cross-correlation between the CMB lensing potential measured by Planck and high-redshift Herschel-ATLAS galaxies 20m
        We present the first measurement of the correlation between the map of the CMB lensing potential derived from the Planck mission data and high-redshift galaxies detected by the Herschel-ATLAS (H-ATLAS) survey. This galaxy catalogue is the highest redshift sample for which the correlation between Planck CMB lensing and tracers of large-scale structure has been investigated so far. We perform a number of null tests and reject the no CMB lensing-galaxy correlation hypothesis at a 20σ significance. The significance of the detection of the theoretically expected cross-correlation signal is found to be 10σ. The estimated galaxy bias, b=2.8 ± 0.1, is consistent with earlier estimates of the bias for the H-ATLAS galaxies at similar redshift. On the other hand, the amplitude of the cross-correlation is found to be a factor 1.6 ± 0.2 higher than expected from the standard model and found by cross-correlation analyses with other tracers of the large-scale structure. We have investigated few possible reasons for the excess amplitude however any of them can not fully account for the enhanced cross-correlation signal.
        Speaker: Pawel Bielewicz (SISSA, Italy)
      • 17:10
        Non-local bias in the halo bispectrum with primordial non-Gaussianity 20m
        Primordial non-Gaussianity can lead to a scale-dependent bias in the density of collapsed halos relative to the underlying matter density. The galaxy power spectrum already provides constraints on local-type primordial non-Gaussianity complementary those from the cosmic microwave background (CMB), while the bispectrum contains additional shape information and has the potential to outperform CMB constraints in future. We develop the bias model for the halo density contrast in the presence of local-type primordial non-Gaussianity, deriving a bivariate expansion up to second order in terms of the local linear matter density contrast and the local gravitational potential in Lagrangian coordinates. Nonlinear evolution of the matter density introduces a non-local tidal term in the halo model. Furthermore, the presence of local-type non-Gaussianity in the Lagrangian frame leads to a novel non-local convective term in the Eulerian frame, that is proportional to the displacement field when going beyond the spherical collapse approximation. We use an extended Press-Schechter approach to evaluate the halo mass function and thus the halo bispectrum. We show that including these non-local terms in the halo bispectra can lead to corrections of up to 25% for some configurations, on large scales or at high redshift.
        Speaker: Matteo Tellarini (ICG, Portsmouth, United Kingdom)
      • 17:30
        The bispectrum of relativistic galaxy number counts 20m
        In this talk, I will present the evaluation of the galaxy number counts to second order in cosmological perturbation theory in the Poisson gauge. The calculation is performed using an innovative approach based on the recently proposed ”geodesic light-cone” gauge, which allows us to determine the number counts in a purely geometric way. To conclude, I will present the numerical results for the leading non-linear and relativistic contributions to the number counts bispectrum, comparing them with the usual term from weakly non-linear Newtonian gravitational clustering and showing how to neglect integrated relativistic terms can bring significant bias.
        Speaker: Giovanni Marozzi (Universite de Geneve, Switzerland)
      • 17:50
        Primordial black holes as biased tracers 20m
        Primordial black holes (PBHs) are theoretical black holes which can be formed during the radiation dominant era through the gravitational collapse of radiational overdensities. It has been well known that in the context of the structure formation in our Universe such collapsed objects, e.g., halos/galaxies, could be considered as bias tracers of underlying matter fluctuations and the halo/galaxy bias has been studied well. Applying such a biased tracer picture to PBHs, we investigate the large scale clustering of PBHs and obtain an almost mass-independent constraint to the scenario that the dark matter (DM) consists of PBHs. We focus on the case where the statistics of the primordial curvature perturbations is almost Gaussian, but with small local-type non-Gaussianity. If PBHs account for the DM abundance, such a large scale clustering of PBHs behaves as nothing but the matter isocurvature perturbation which is strictly constrained by the observations of cosmic microwave backgrounds (CMBs). From this constraint, we show that, in the case where a certain single field causes both CMB temperature perturbations and PBH formation, the PBH-DM scenario is excluded even with quite small local-type non-Gaussianity, |fNL| ∼ O(0.01).
        Speaker: Yuichiro Tada (Kavli IPMU, Japan)
    • 16:10 18:10
      Dark Energy: DE Rm 115+116 ()

      Rm 115+116

      Convener: David Polarski
      • 16:10
        Quasi-Static Solutions for Compact Objects in Chameleon Models 20m
        It has been suggested that a scalar field φ non-minimally coupled to matter could be responsible for the observed accelerated expansion of the Universe. However, the fact that we are able to measure its effect only on cosmological scales but not on local ones, such as that of our solar system, might be the consequence of a screening mechanism. This is the essence of the Chameleon model. Understanding its viability requires solving the field equations in the transition regime where the scalar field transitions from a region of high density to the outer region where it plays the role of the Dark Energy. In this work we analyze quasi-static spherically symmetric solutions for objects such as standard stars and more compact objects like white dwarfs and neutron stars, by solving the Tolman-Oppenheimer-Volkoff equations coupled with the Klein-Gordon equation in a quasi static regime. We derive a solution that takes into account the background expansion without needing to introduce an artificial cosmic matter corresponding to a non-spatially flat metric. The interior of the star is characterized using a polytropic equation of state while outside we consider a dark matter halo with a Navarro-Frenk-White density profile until it matches onto the cosmic density of an expanding spatially flat background.
        Speaker: Ilia Musco (LUTH - Observatoire de Paris, France)
      • 16:30
        String Gas Cosmology with Varying Spped of Light 20m
        Some years ago in the context of a mechanism that thermally generates the primordial perturbations through a Hagedorn phase of string cosmology (Nayeri-Brandenberger-Vafa (NBV) setup) a blue tensor tilt with an induced and complimentary red tilt to the scalar spectrum, with a naturally large tensor to scalar ratio that relates to both, was found. One of the shortcomings of this setup, however, is assuming a universe, which is flat and big enough to account for the present size of the current observable universe. To fix this issue, the constancy of speed of light during the Hagedorn phase only is being relaxed and assumed to be to be the function of the running dilatonic field in that era. By the end of the Hagedorn epoch the speed of light is fixed and the universe transits to the radiation dominated long before Nucleosynthesis. This ansatz solves the so called flatness problem of the string gas cosmology in the NBV setup.
        Speaker: Ali Nayeri (Chapman University, United States)
      • 16:50
        The two faces of mimetic Horndeski gravity: disformal transformations and Lagrange multiplier 20m
        P. Karmakar, in collaboration with: F. Arroja, N. Bartolo and S. Matarrese (arXiv:1506.08575). We show that very general scalar-tensor theories of gravity (including, e.g., Horndeski models) are generically invariant under disformal transformations. However there is a special subset, when the transformation is not invertible, that yields new equations of motion which are a generalization of the so-called \mimetic" dark matter theory recently introduced by Chamsedinne and Mukhanov. These conclusions hold true irrespective of whether the scalar eld in the action of the assumed scalar-tensor theory of gravity is the same or dierent than the scalar eld involved in the transformation. The new equations of motion for our general mimetic theory can also be derived from an action containing an additional Lagrange multiplier eld. The general mimetic scalar-tensor theory has the same number of derivatives in the equations of motion as the original scalar-tensor theory. As an application we show that the simplest mimetic scalar-tensor model is able to mimic the cosmological background of a at FLRW model with a barotropic perfect fluid with any constant equation of state.
        Speaker: Purnendu Karmakar (Universita degli Studi di Padova, Italy)
      • 17:10
        Random potentials in Cosmology 20m
        Moduli spaces in string theory, often dubbed Landscapes, are usually of high dimensionality and feature a complicated potential. Is multi-field inflation on such landscapes consistent with current observations? Modeling such landscapes by random potentials offers the opportunity to asses generic features of inflation. Random matrix theory provides a tool (complementing numerical experiments) to address many questions analytically, without requiring a detailed knowledge of the potential, i.e. details of the compactification, due to the feature of universality. Thus, generic prediction of a landscape in string theory can be attained and put to the test. I will discuss novel techniques to construct random potentials locally by a generalization of Dyson Brownian motion, explain some predictions, such as the preference of saddle point inflation in a class of landscapes, and comment on the role of eternal inflation, anthropic arguments and the measure problem within this framework as time permits.
        Speaker: Thorsten Battefeld (University of Goettingen, Germany)
      • 17:30
        Initial conditions for simulations of arbitrary modified gravity, beyond quasi-static approximations 20m
        I will present a novel description for setting initial particle displacements and field values under arbitrary metric theories of gravity, for perfect and imperfect fluids with arbitrary characteristics. We extend the Zel'dovich Approximation to nontrivial theories of gravity, and show how scale dependence implies curved particle paths, even in the entirely linear regime of perturbations. Initial conditions set at high redshifts are affected at the level of up to 5% at Mpc scales, which exemplifies the importance of going beyond ΛCDM initial conditions for modifications of gravity outside of the quasi-static approximation. Our description paves the way for simulations and mock galaxy catalogs under theories of gravity beyond the standard model, crucial for progress towards precision tests of gravity and cosmology.
        Speaker: Wessel Valkenburg (Leiden University, Netherlands)
      • 17:50
        Covariantised Vector Galileons 20m
        Vectors with ghost-free derivative self-interactions have been shown to have interesting cosmological applications. They form a ghost-free extension of the Proca theory that has a Galileonic longitudinal mode and can be generated naturally via a Higgs mechanism. In this talk I will discuss recent results on the covariantisation of these models and their relation to general ghost-free scalar-tensor theories.
        Speaker: Mathew Hull (University of Portsmouth, United Kingdom)
    • 16:10 18:10
      Dark Matter: DM Rm 207 ()

      Rm 207

      Convener: Kiwoon Choi
      • 16:10
        Newtonian linear perturbations from the Schroedinger-Poisson equations 20m
        Dark matter is a crucial ingredient of the standard cosmological model, making up over 80% of the total matter in the Universe. Although observational evidence strongly favors the existence of dark matter, we are yet to physically detect a particle, despite many attempts to do so. In order to model the dynamics of structure formation with dark matter one uses Newtonian physics, where we are able to understand much in the linear regime. While this is reliable for WIMPs, it is not necessarily the case for other candidates. In particular, for the axion, one might expect that this description as a classical, pressureless fluid is incomplete, since the axion is really a quantum field. In this talk I will describe work done on the first step towards the goal of describing structure formation with axions. Namely, I will show that the wavefunction approach reproduces the usual evolution equation for the density perturbation, albeit with an additional term dubbed the 'quantum pressure' term. I will close with a discussion of limitations of the approach, and plans for future work.
        Speaker: Adam Christopherson (University of Florida, United States)
      • 16:30
        IceCube potential for detecting Q-ball dark matter 20m
        We study Q-ball dark matter in gauge-mediated supersymmetry breaking, and seek the possibility of detection in the IceCube experiment. We find that the Q balls would be the dark matter in the parameter region different from that for gravitino dark matter. In particular, the Q ball is a good dark matter candidate for low reheating temperature, which may be suitable for the Affleck-Dine baryogenesis and/or nonthermal leptogenesis. Dark matter Q balls are detectable by IceCube-like experiments in the future, which is the peculiar feature compared to the case of gravitino dark matter.
        Speaker: Shinta Kasuya (Kanagawa University, Japan)
      • 16:50
        Constraining the dark matter by 21cm signals 20m
        The future prospects for the constraints on the particle dark matter from the 21cm signals will be presented. The effects of the dark matter interactions with the baryons on the 21 cm observables will be discussed, along with its comparison with the complementary bounds from the direct dark matter search experiments. I will also discuss the 21 cm bounds on the ultra light dark matter which can ubiquitously arise in the early Universe, such as pseudo-Goldstone bosons from the spontaneous breaking of an approximate symmetry.
        Speaker: Kenji Kadota (Institute for Basic Science, Republic of Korea)
      • 17:10
        Super-weakly interacting Dark Matter 20m
        I will review model-independent bounds on the properties of DM particles and the current state of searches for the signatures of decayingh super-weakly intercating DM particles in astrophysical data.
        Speaker: Alexey Boyarsky (Leiden University, Netherlands)
      • 17:30
        Constraining the lifetime of Dark Matter 20m
        The existence of Dark Matter has been confirmed by many different cosmological probes including observations of the Cosmic Microwave Background (CMB) and the Large Scale Structure (LSS) of the Universe. But what else can we learn about the nature of Dark Matter from CMB and LSS data? One parameter of interest is the decay rate of Dark Matter. Even though Dark Matter must be stable on cosmological time scales, it may not be absolutely stable. If we know the decay channels of the Dark Matter particle we can derive bounds on the decay rate by looking for visible decay products. But any such bound will of course depend on the assumed particle physics model. However, we can derive a model-independent bound if we assume the ‘worst-case’ scenario that Dark Matter only decay into invisible relativistic particles. To be truly model-independent we also extend the cosmological model by parameters, which could be degenerate with the Dark Matter decay rate.
        Speaker: Thomas Tram (ICG Portsmouth University, United Kingdom)
      • 17:50
        A stable Higgs portal with vector dark matter 20m
        We explored an extension of the Standard Model by an additional U(1) gauge group and a complex scalar interacting through the Higgs portal. As the scalar is charged under this gauge factor, this simple model supplies a vector dark matter candidate satisfying the observed relic abundance and limits from direct dark matter searches at LUX and XENON. An additional Higgs-like state, that may be heavier or lighter than the observed Higgs, is present and fulfills LEP and LHC bounds. We performed a detailed analysis of the running of the couplings and found a region in the parameter space that allows for the absolute stability of the electroweak vacuum.
        Speaker: Mateusz Duch (University of Warsaw, Poland)
    • 16:10 18:10
      Inflation and phase transitions: Inflation + PT Rm 111+112 ()

      Rm 111+112

      Convener: Arttu Rajantie
      • 16:10
        Inflation and dark energy from alpha-attractors 20m
        The Planck value of the spectral index can be interpreted as ns=1−2/N in terms of the number of e-foldings N. An appealing explanation for this phenomenological observation is provided by α-attractors: the inflationary predictions of these supergravity models are fully determined by the curvature of the Kahler manifold. We provide a unified description of cosmological α-attractors and late-time acceleration. Our construction involves two superfields playing distinctive roles: one is the dynamical field and its evolution determines inflation and dark energy, the other is nilpotent and responsible for a landscape of vacua and supersymmetry breaking. We prove that the attractor nature of the theory is enhanced when combining the two sectors: cosmological attractors are very stable with respect to any possible value of the cosmological constant and, interestingly, to any generic coupling of the inflationary sector with the field responsible for uplifting.
        Speaker: Marco Scalisi (Van Swinderen Institute - University of Groningen, Netherlands)
      • 16:30
        Consistency relations for features in the primordial spectra 20m
        We discuss the generation of sharp features in the primordial spectra within the framework of effective field theory of inflation, wherein curvature perturbations are the consequence of the dynamics of a single scalar degree of freedom. We identify two sources in the generation of features: the time-variation of the sound speed of curvature fluctuations c_s and the time-variation of the expansion rate H during inflation. We propose a non-trivial relation between these two quantities that allows us to study the generation of features in realistic scenarios where features are the result of the simultaneous occurrence of these two sources. This relation depends on a single parameter with a value determined by the model responsible for the time-varying background. As a consequence, we deduce a one-parameter consistency relation between the shape and size of features in the bispectrum in terms of those of features in the power spectrum. This relation constitutes a powerful tool to parametrize and study the appearance of features in the power spectrum, and offers a concrete prediction for the search of features in future large scale structure. To support this result, we discuss several examples of models where the one-parameter relation between the c_s and H is satisfied. In addition, we discuss the particular case of resonant features, for which Planck is already able to constrain our consistency relation.
        Speaker: Gonzalo Palma (FCFM, Universidad de Chile, Chile)
      • 16:50
        Spacetime curvature and the Higgs stability before and after inflation 20m
        The best fit values for the SM parameters imply that the potential for the Higgs boson developes a Planck-scale vacuum with negative energy, which may result in decay of the current vacuum state. In this talk we show the significance of backreaction from classical gravity for vacuum stability during and after inflation. In particular we show that requiring stability, inflation constrains the non-minimal coupling between the SM Higgs and gravity to be larger than ~ 0.1 whereas reheating constrains it to be smaller than ~ 1, if the scale of inflation is large. arXiv:1407.3141 and arXiv:1506.04065.
        Speaker: Tommi Markkanen (Imperial College, United Kingdom)
      • 17:10
        Generation and evolution of cosmological magnetic fields at the electroweak epoch 20m
        In this talk I will present new results about generation and evolution of cosmological magnetic fields, showing that some of our basic assumptions about the primordial plasma are violated when helical magnetic fields are present in it. The consequences for survival of the magnetic fields and effects on the processes like leptogenesis will also be discussed.
        Speaker: Oleg Ruchayskiy (EPFL, Switzerland)
      • 17:30
        Heavy neutrinos in cosmology and particle physics 20m
        We study experimental and cosmological constraints on the extension of the Standard Model by three right handed neutrinos with masses between those of the pion and W-boson. This low scale seesaw scenario allows to simultaneously explain the observed neutrino oscillations and the baryon asymmetry of the universe. We combine indirect experimental constraints from neutrinoless double β-decay, lepton flavour violation and neutrino oscillation data with bounds from past direct searches and big bang nucleosynthesis. For masses of a few GeV the heavy right handed neutrinos can be found in meson decays at LHCb, BELLE II or the proposed SHiP experiment, for larger masses they can be searched for in ATLAS and CMS. The chances for a discovery would be even better at a Future Circular Collider.
        Speaker: Marco Drewes (TU Munich, Germany)
      • 17:50
        Particle production after inflation with non-minimal derivative couplings to gravity 20m
        Speaker: Yohei Ema (The University of Tokyo, Japan)
    • 19:30 22:00
      Panel discussion 2h 30m Main Hall ()

      Main Hall

    • 09:00 10:10
      Plenary Main Hall ()

      Main Hall

      Convener: Hans-Peter Nilles
    • 10:10 10:40
      Coffee 30m
    • 10:40 12:40
      Plenary Main Hall ()

      Main Hall

      Convener: Katherine Freese
      • 10:40
        Realisations of de Sitter space and inflation in string compactifications 35m
        Speaker: Fernando Quevedo (The Abdus Salam International Centre for Theoretical Physics, Italy)
      • 11:15
        Searches for new physics at the LHC 35m
        Speaker: Livia Soffi (Cornell University, United States)
      • 11:50
        From precision spectroscopy to fundamental cosmology: current and future tests of the stability of fundamental couplings 35m
        Speaker: Carlos Martins (CAUP, Portugal)
      • 12:25
        Outlook 15m
        Speaker: Leszek Roszkowski (National Centre for Nuclear Research, Poland)
    • 12:40 14:00
      Lunch 1h 20m
    • 14:00 15:40
      CMB, LSS and cosmological parameters: CMB + LSS Main Hall ()

      Main Hall

      Convener: Bożena Czerny
      • 14:00
        A convergent perturbation theory for Newtonian cosmological structure formation 20m
        Analytical methods have been fairly successful to understand the Newtonian regime of cosmological structure formation. Such methods are usually based on standard perturbation techniques which are however only approximative tools, and therefore might be not able to achieve the required accuracy to confront the theory with data from upcoming surveys. In this talk we show that it is actually possible to solve exactly for the non-linear fluid equations, if we consider an alternative approach to conventional perturbation theory. Indeed, in this talk it is shown that in a flat, cold dark matter (CDM) dominated Universe with positive cosmological constant (Λ), particle trajectories are analytical in time (representable by a convergent Taylor series) until at least a finite time after decoupling. The time variable used for this statement is the cosmic scale factor, i.e., the "a-time", and not the cosmic time. For this, a Lagrangian-coordinates formulation of the Euler-Poisson equations is employed. Temporal analyticity for ΛCDM is found to be a consequence of novel explicit all-order recursion relations for the a-time Taylor coefficients of the Lagrangian displacement field, from which we derive the convergence of the a-time Taylor series.
        Speaker: Cornelius Rampf (Portsmouth University, United Kingdom)
      • 14:20
        Measuring CMB Polarization with POLARBEAR and the Simons Array: Towards New Constraints on Neutrino Masses and Inflation 20m
        Measurements of the polarization of the cosmic microwave background (CMB) are rapidly becoming an important tool to test the standard model of cosmology. In particular, searches for the faint CMB B-mode signals offer the prospect of detecting inflationary gravitational waves on large angular scales and mapping out the large scale distribution of matter in the Universe through CMB lensing on smaller angular scales. POLARBEAR is a CMB polarization experiment located in the Atacama desert in Chile that has been pursuing both goals since 2012. The Simons Array is an expansion of the POLARBEAR experiment to three 3.5 meter telescopes with new multi-chroic receivers. The first of these new receivers, POLARBEAR-2, will have first light in 2016. With exceptional sensitivity in multiple frequency bands and planned coverage of two thirds of the sky, the Simons Array will yield a high signal-to-noise mass map across most of the sky. Combining CMB lensing data from the Simons Array with future baryon acoustic oscillation data results in a 1-sigma constraint on the sum of the neutrino masses of 19 meV when foregrounds are ignored, increasing to 40 meV when including component separation and foreground residuals. Even after foreground separation, the Simons Array will be able to measure tensor-to-scalar ratios (r) as low as r = 0.014 at 2-sigma. We present the status of this funded instrument and its expected capabilities.
        Speaker: Christian Reichardt (University of Melbourne, Australia)
      • 14:40
        The structure of the real line and cosmology 20m
        We discuss the recently proposed model where LSS of spacetime is parametrized by the usual real line R, while at small (QM) scales space is parametrized by real numbers from RM. Here RM is the real line in certain model M of formal Zermelo-Fraenkel set theory. When passing from RM to R the set-theoretic forcing on measure algebra of R3 has to be performed. The "old" set of reals RM is merely a meager subset of R. Moreover, it has the Lebesgue measure 0. This irregular meager set of reals describes space at the Planck era. From the point of view of the enlarged by forcing model M[G] with the "new" reals RM[G], the set RM⊂RM[G] is irregular. We consider the possible role of these irregularities in the scenario where primordial quantum fluctuations lead to the subsequent structure formation. The effects of such irregularities on the eventual distortions in the CMB are also discussed.
        Speaker: Pawel Klimasara (University of Silesia, Poland)
      • 15:00
        Post-Newtonian Cosmological Modelling 20m
        We construct a framework to probe the effect of non-linear structure formation on the large-scale expansion of the universe. We take a bottom-up approach to cosmological modelling by splitting up our universe into cells. The matter content within each cell is described by the post-Newtonian formalism. We assume that most of the cell is in the vicinity of weak gravitational fields, so that it can be described using a perturbed Minkowski metric. Our cells are patched together using the Israel junction conditions. We impose reflection symmetry across the boundary of these cells. This allows us to calculate the equation of motion for the boundary of the cell and, hence, the expansion rate of the universe. At Newtonian order, we recover the standard Friedmann-like equations. At post-Newtonian orders, we obtain a correction to the large-scale expansion of the universe. Our framework does not depend on the ambiguous process of averaging in cosmology.
        Speaker: Viraj Sanghai (Queen Mary University of London, United Kingdom)
      • 15:20
        The decay of primordial magnetic fields and CMB spectral distortions 20m
        We calculate the CMB spectral distortions due to the decay of causally generated magnetic fields at the electroweak and QCD phase transitions. We show that the decay of non-helical magnetic fields generated at either the electroweak or QCD scale produce μ and y-type distortions below 10^−8 which are probably not detectable by a future PIXIE-like experiment. We show that magnetic fields generated at the electroweak scale must have a helicity fraction f∗>10^−4 in order to produce detectable μ-type distortions. Hence a positive detection coming from the decay of magnetic fields would rule out non-helical primordial magnetic fields and provide a lower bound on the magnetic helicity.
        Speaker: Jacques Wagstaff (Hamburg University, Germany)
    • 14:00 15:40
      Inflation and phase transitions: Inflation Rm 111+112 ()

      Rm 111+112

      Convener: Marek Demiański
      • 14:00
        Gravitational effects on inflaton decay 20m
        Inflaton inevitably couples to all non-conformally coupled matters to gravity, through an oscillation in the Hubble parameter or the cosmic scale factor. This coupling leads to particle production during the inflaton oscillation regime even in the minimal (Einstein-Hilbert action + canonical inflaton) setup. In addition, such particle production due to the oscillation in the Hubble parameter can be more efficient in models with non-minimal inflaton couplings to gravity. I will illustrate scalar particle production and graviton production from the inflaton due to this mechanism.
        Speaker: Ryusuke Jinno (The University of Tokyo, Japan)
      • 14:20
        Production of magnetic fields in axion inflation and their post-inflationary evolution 20m
        There has recently been a growing evidence for the existence of magnetic fields in the extra-galactic regions, while the attempt to associate it only with the inflationary epoch has been found extremely challenging. We thus take into account the post-inflationary evolution of the magnetic fields originated from vacuum fluctuations during inflation. We consider the model in which the inflaton is a pseudo scalar and is coupled to the electromagnetic (EM) field through the term allowed by the symmetries. This interaction dynamically breaks parity and induces the continuous production of a helical EM field through tachyonic instability. The dominant contribution to the observed magnetic fields in this model comes from the modes that leave the horizon near the end of inflation, further enhanced right after the end of inflation. The EM field is subsequently amplified by parametric resonance during the period of inflaton oscillation. Once reheating occurs, the produced helical magnetic fields undergo a turbulent process called inverse cascade, which shifts their peak correlation from smaller to larger scales. We take all these effects into account in a self-consistent manner and obtain the magnetic fields with the effective strength of order 10−19 G. While this effect is present in any models with a pseudo-scalar inflaton, our result indicates the necessity of additional mechanisms to accommodate the observations.
        Speaker: Ryo Namba (Kavli IPMU, Japan)
      • 14:40
        Generation of sparse and localized curvature perturbation from inflation 20m
        We propose a mechanism of producing new type of primordial perturbation from which primordial black holes whose mass is comparable to the supermassive black holes observed at high redshifts are produced. The observable Universe consists of two kinds of many small patches which experienced different history during inflation. Large amplitude of the primordial perturbation enough to form primordial black hole is generated on patches that experienced more Hubble expansion than the others. By making the former patches minor component, rarity of supermassive black holes is explained. Most region of the Universe belongs to the major history and has only standard adiabatic perturbation at the same level of the large scale value. Thus our mechanism can evade the constraint from the non-detection of the CMB distortion set by the COBE/FIRAS measurement. Prediction of our scenario which can be tested by future observations is also discussed.
        Speaker: Teruaki Suyama (Research Center for the Early Universe, University of Tokyo, Japan)
      • 15:00
        Warm quartic inflation in light of Planck 2015 results 20m
        In the present work we show that warm chaotic inflation characterized by a simple $\frac{\lambda}{4}\phi^{4}$ self-interaction potential for the inflaton, excluded by current data in standard cold inflation, and by an inflaton decay rate proportional to the temperature, is in agreement with the latest Planck data. The parameters of the model are constrained, and our results show that the model predicts a negligible tensor-to-scalar ratio in the strong dissipative regime, while in the weak dissipative regime the tensor-to-scalar ratio can be large enough to be observed.
        Speaker: Grigorios Panotopoulos (Department of Physics, University of Chile, Chile)
      • 15:20
        Influence of interactions terms on non-perturbative particle production and preheating 20m
        We have investigated effects of interaction terms on non-perturbative particle production. It is well known that a time-varying background induces abundant particle production, such as the preheating theory. As our conclusion, it is possible to induce particle production even if particles do not couple to the background directly. Such particles are produced through the interactions with other fields, which couple to a varying background. In this talk, we will demonstrate with a simple but illustrative model and discuss the influence of the discussed mechanism on preheating.
        Speaker: Seishi ENOMOTO (Faculty of Physics, University of Warsaw, Poland)
    • 14:00 15:40
      Inflation and phase transitions: PT Rm 115+116 ()

      Rm 115+116

      Convener: Mariusz Dąbrowski
      • 14:00
        Scale Invariant Top Condensate Model 20m
        We propose a minimal, scale invariant model for dynamical electroweak symmetry breaking via top condensation. The classical scale invariance is realized nonlinearly by introducing conformal compensator scalar field, the (pseudo)dilaton, which plays crucial role in a successful prediction for the Higgs boson and top quark masses. We also argue that the fine-tuning problem of the ordinary top condensate scenario is resolved in our model.
        Speaker: Shelley Liang (School of Physics, University of Sydney, Australia)
      • 14:20
        Primordial magnetic fields from cosmic defects 20m
        A symmetry-breaking phase transition in the early universe could have led to the formation of cosmic defects. Because these defects dynamically excite not only scalar and tensor type cosmological perturbations but also vector type ones, they may serve as a source of primordial magnetic fields. In this study, we calculate the time evolution and the spectrum of magnetic fields from two types of cosmic defects, called global texture and cosmic string. To see cosmological scale magnetic fields, here we use the non-linear sigma model for the texture model and infinite string for the cosmic string model. Based on the standard cosmological perturbation theory, we show that relative velocity between photon and baryon fluids induced by the cosmic defects could lead to magnetic field generation over a wide range scale inevitably.
        Speaker: Kouichirou Horiguchi (Nagoya University, Japan)
      • 14:40
        QCD corrections to Leptogenesis 20m
        Thermal Leptogenesis gives a simple and elegant solution to the baryon asymmetry in the universe problem. In this scenario the CP-violating thermal decay of a very massive Majorana neutrino accounts for this asymmetry. This mechanism requires high temperature and a strongly coupled electro-weak primordial bath. We will show a novel way to treat corrections that arises when the strong interactions of the bath are taken into account by using the collinear-thermal-loop resummation developed in QCD. We will also compare our results obtained in the Kadanoff-Baym formalism with the semi-classical Boltzmann approach.
        Speaker: Sebastian Mendizabal (Universidad Tecnica Federico Santa Maria, Chile)
      • 15:00
        Cosmology With Negative Absolute Temperatures 20m
        Negative absolute temperatures are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al (Science, 2013) has not only rekindled interest in these counter-intuitive regimes but also sparked a debate which has forced a revision of the very foundations of statistical physics. The purpose of this talk is to provide the first ever (as far as we are aware) discussion of the possible cosmological relevance of these phenomena. In particular, we shall investigate how they naturally give rise to an inflationary epoch and address the challenges to successfully ending inflation in these types of scenarios.
        Speaker: Jose Pedro Pinto Vieira (Mathematical and Physical Sciences, University of Sussex, United Kingdom)
      • 15:20
        Helical Magnetic Fields from Creation to Detection 20m
        It is customary and often necessary to study cosmological phase transitions, such as inflation and thermal symmetry-breaking phenomena, through the relics they leave behind. A relic magnetic field, for instance, could have been sustained by the hot plasma of the early universe and provide the seed for galactic-scale fields seen today. Evidence for this primordial magnetic field may be found in the voids between the galaxy clusters where the field survives unprocessed by structure formation. Ongoing efforts by gamma ray telescopes hope to reveal a magnetically-broadened electromagnetic cascade halo around TeV gamma ray sources such as blazars. I will discuss how measurements of the halo morphology can be used to probe not only the magnetic field strength, but also its helicity and coherence length. Helical magnetic fields, having a larger field amplitude in either left- or right-circular polarization modes, are predicted by models of pseudoscalar inflation as well as models of baryogenesis, and in the latter scenario, the sign of the helicity is determined by the sign of the baryon asymmetry. Thus a detection of helical magnetic fields in intergalactic space would open a new chapter in early universe cosmology, and efforts are already underway to make such a measurement possible.
        Speaker: Andrew Long (KICP, United States)
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