Progress on Old and New Themes in cosmology (PONT) 2014

Apr 14, 2014, 8:00 AM → Apr 18, 2014, 2:30 PM Europe/Paris

Chambre du Trésorier (Palais des Papes, Avignon)

The conference addressed the cardinal issues of the dark universe today, gathering a selected number of scientists working in cosmology and particle physics in the inspiring and monumental setting of Avignon. There was a limited number of review talks by leading experts in each field and selected contributed talks, fostering thorough debates. Some time was allocated to discussion sessions.
 

Monday 14: special session on Inflation & BICEP2 (overview talks, dedicated talks and round table). 

Organizers:  
   Philippe Brax (CEA IPhT Saclay)
   Chiara Caprini (CNRS IPhT Saclay)
   Marco Cirelli (CNRS IPhT Saclay)
   Géraldine Servant (IFAE Barcelona)

Practical info intro.pdf

Monday, April 14

9:00 AM → 12:30 PM 1-Inflation and CMB

9:00 AM Planck 2013 cosmology results

I review the main cosmology results from the 2013 Planck release. I will also discuss some developments since the original submission of the papers, and put the Planck results in the context of more recent results from the CMB and other cosmological and astrophysical datasets.

Speaker: Anthony Challinor (University of Cambridge)

Slides Avignon2014.pdf

9:45 AM Inflation after BICEP2

Speaker: Daniel Baumann

Slides Baumann-Avignon.key

10:30 AM Coffee Break

11:00 AM Testing inflation after Planck

TBA

Speaker: Dr christophe ringeval (CP3, Louvain U.)

Slides Ringeval.pdf

11:45 AM What is left of non-Gaussianity?

I will discuss the status of primordial non-Gaussianity after the release of Planck 2013 data. Specific models for the primordial bispectrum are now tightly constrained, while higher-order correlators remain only weakly bounded. Non-linear evolution does generate non-Gaussianity and the challenge remains to separate out the intrinsic non-Gaussianity imprinted in the cosmic microwave background and large-scale structure from primordial non-Gaussianity from inflation (or other scenarios for the origin of structure).

Speaker: David Wands (University of Portsmouth)

Slides Wands-PONT2014.pdf Wands-PONT2014.ppt

12:30 PM → 2:30 PM Lunch Break

2:30 PM → 3:15 PM 1-Inflation and CMB

2:30 PM The stability of the electroweak vacuum

Speaker: Jose Espinosa (Departm.of Physics & Astronomy)

Slides PONT14Espinosa.pdf

3:15 PM → 6:15 PM Afternoon session

3:15 PM Closing in on Axion Dark Matter

The axion is well motivated dark matter candidate with a very different phenomenology than WIMPs. It is produced non-thermally in the early universe and its low mass, $m_a<$meV, and feeble interactions makes its detection very demanding, requiring highly specialised experiments for even slightly different axion masses. In this talk I review the predictions for the axion mass focusing on the standard-thermal-scenario (where axion strings and domain walls contribute significantly to the DM abundance) and discuss the experimental possibilities for its detection, in a region which has been foolishly neglected, and turns out to be the most relevant if the BICEP2 claim of detection of primordial waves is confirmed. The only relevant experiment to look for axions in the mid-future seems to be the recently proposed International AXion Obserbatory (IAXO), which can search for solar axions, and which will be also briefly touched upon in the talk.

Speaker: Javier Redondo (LMU/MPP Munich)

Slides RedondoPONT.pdf

3:45 PM UV-completing Ghost Inflation

We present a setup that provides a UV-completion of the ghost inflation model up to a scale which can be almost as high as the Planck mass. This is achieved by coupling the inflaton to the Lorentz-violating sector described by the Einstein-aether theory or its khronometric version. Compared to previous works on ghost inflation our setup allows to go beyond the study of small perturbations and include the background dynamics in a unified framework. In the specific regime when the expansion of the Universe is dominated by the kinetic energy of the inflaton we find that the model predicts rather high tensor-to-scalar ratio r ~ 0.1 and non-Gaussianity of equilateral type with f_NL ~ -40.

Speaker: Sergey Sibiryakov (CERN & EPFL)

Slides PontdAvignon2014.pdf

4:05 PM The full CMB temperature bispectrum from single-field inflation

CMB non-Gaussianity can be used to discriminate between models of the early universe. However, to correctly measure a primordial signal we must remove any contamination from intrinsic non-linear effects intervening between the initial conditions and the CMB anisotropies. I will compute these effects, first when one of the momenta is much smaller than the others (squeezed limit) and then with a full second-order calculation using the Boltzmann COSMOLib2nd. I will then discuss their observability and their contamination to measurement of a primordial signal.

Speaker: Dr Filippo Vernizzi (IPhT, CEA/Saclay)

Slides Avignon_Pont_2014.pdf

4:25 PM Coffee Break

4:55 PM Minimal models for inflation

Experimental results of the past several years favor the very minimal inflationary models. I will discuss some realizations of inflation in minimal extensions of the Standard Model, where no new scales are present between the Electroweak scale and inflationary scale and the amount of new particles is minimal -- Higgs inflation, $R^2$ inflation, non-minimally coupled inflation with light inflaton. I'll discuss the advantages and problems with the models, and experimental features predicted for cosmology and particle physics.

Speaker: Fedor Bezrukov (UConn & CERN & BNL)

Slides MinimalInflationModels.pdf

5:15 PM Non-gaussian imprints of primordial magnetic fields from inflation

If cosmic magnetic fields are produced during inflation, they are likely to be correlated with the primordial curvature perturbations that are responsible for the Cosmic Microwave Background anisotropies and Large Scale Structure. We compute the three-point cross-correlation function of the curvature perturbation with two powers of the electromagnetic field in a typical model of inflationary magnetogenesis. Such a correlation turns out to be non-Gaussian in nature and serves as a new contribution to the non-Gaussian signatures induced by primordial magnetic fields. We show that there exists a new simple consistency relation for such a cross-correlation in the squeezed limit. On the other hand, the signal is maximized for the flattened configuration where the magnetic non-linear parameter becomes as large as O(10^3). Detectability of such a correlation can both provide a new observational window to the underlying theory of cosmic inflation, and also shed light on the origin of cosmic magnetic fields.

Speaker: Rajeev Kumar Jain (CP3-Origins)

Slides talk-avignon.pdf

5:35 PM Searching for primordial correlations between the magnetic field and the density perturbation using \mu-distortion

Damping of non-uniform magnetic field between redshifts of about $10^4$ and $10^6$ cause the observed CMB to deviate from a perfect blackbody spectrum, producing a so-called $\mu$-distortion. This allows us to search for a correlation $\langle\zeta B^2\rangle$ between the magnetic field $B$ and the density perturbation $\zeta$ by looking for a $\mu T$ correlation in the CMB, where $T$ is the temperature perturbation. Since the magnetic field perturbations, which produce $\mu$-distortion, will be much smaller scale than the density perturbations, this observable is sensitive to the local limit of $\langle\zeta B^2\rangle$, naturaly parametrized by $b_{NL}$, a parameter defined analogously to $f_{NL}$. We discuss the observability of $b_{NL}$ by CMB experiments. We also discuss post magnetogenesis-era sources of a $\langle\zeta B^2\rangle$ correlation.

Speaker: Mr Jonathan Ganc (CP3-Origins, University of Southern Denmark)

Slides Ganc.pdf

5:55 PM A new consequence of Inflation: Imprinting the Standard Model in the sky

The existence of the Standard Model (SM) Higgs implies that a gravitational wave (GW) background is generated, soon after the end of inflation, by the decay products of the Higgs. Theoretically all Yukawa and SU(2) gauge couplings of the SM are imprinted as features in the GW spectrum. In practice, the signal from the most strongly coupled species dominates, rendering inaccesible the information on the other species. If detected, this background could be used for measuring properties of high-energy particle physics, including beyond the SM. To achieve this goal, new high frequency detection technology is required, beyond that of currently planned detectors.

Speaker: daniel figueroa

Slides DaniFigueroa.pdf

6:20 PM → 7:20 PM Round Table Discussion on inflation and BICEP2

Conveners: Anthony Challinor, Christophe RINGEVAL, Daniel BAUMANN, David Wands (University of Portsmouth), Hiranya Peiris (University College London), Lorenzo Sorbo (University of Massachusetts, Amherst)

7:20 PM → 8:20 PM Welcome cocktail

Tuesday, April 15

9:00 AM → 12:45 PM 2-Astroparticle

9:00 AM Leptogenesis: status and recent progress

I will review the status of leptogenesis and present some recent progress.

Speaker: Stephane Lavignac (Institut de Physique Théorique, CEA-Saclay)

Slides Avignon_150414.pdf

9:45 AM Dark Radiation

I will review the status of dark radiation in the context of cosmology and present some recent progress.

Speaker: Hiranya Peiris (University College London)

Slides Dark_radiation.pdf

10:30 AM Coffee Break

11:00 AM Cosmological magnetic fields

Magnetic fields found in different structures in the Universe, including galaxies and galaxy clusters, are the results of amplification of much weaker magnetic fields which existed before or were generated simultaneously with the process of structure formation. Uncertainty of the origin of the initial weakest magnetic fields at the origin of the amplification process constitutes one of the long-standing problems of astronomy / cosmology. I will review efforts toward resolution of this problem, with an emphasis on the possibilities of observational testing of different cosmological magnetogenesis models.

Speaker: Andrii Neronov (Universite de Geneve (CH))

Slides Neronov_Avignon2014.pdf Neronov_Avignon2014.pptx

11:45 AM Baryogenesis and the EW Phase Transition: some new developments and old connections

TBA

Speaker: Prof. Kimmo Kainulainen (University of Jyvaskyla)

Slides Kainulainen.key Kainulainen.pdf

12:15 PM Dark forces and new physics at the intensity frontier

New physics can be relatively strongly coupled and heavy, or it can be light and very weakly coupled to the SM. In the last five years, the interest to the second possibility has increased thanks to the advances in experimental possibilities to search for such particles at the intensity frontier experiments. Often, these new states are helping theorists to construct more viable dark matter models, and as such are often dubbed as "friends of dark matter" or "dark forces". I will give an overview of some recent developments in this subject, both on experimental and theoretical side.

Speaker: Maxim POSPELOV

Slides pospelov2014.pdf

12:45 PM → 2:30 PM Lunch Break

2:30 PM → 6:30 PM Afternoon session

2:30 PM Gaia: science and status - and an update on ultra-faint feedback

Gaia is in orbit, well into commissioning. I will will give an overview of Gaia's status, and potential to quantify mass distributions on interesting scales. i shall also briefly summarise recent work on chemical evolution in ultrafaint dSph galaxies, and the implications for feedback as a mechanism to perturb - or not - dark matter cusps and cores.

Speaker: Gerry Gilmore (Institute of Astronomy, cambridge,UK)

Slides Gaia-Gilmore-Pont-Avignon-Apr-2014.pdf

3:00 PM Primordial black holes as dark matter candidates: closing the remaining mass window

Primordial black holes (PBH), if they constitute a fraction of dark matter, can be captured by compact stars and lead to a rapid destruction of the latter. Thus, a mere observation of neutron stars and white dwarfs implies constraints on the PBH abundance. We will consider capture of BPH both at the stage of formation of the star and during its lifetime, and derive corresponding constraints.

Speaker: Peter Tinyakov (U)

Slides 2014-Avignon.pdf

3:20 PM Dark Matter Interpretations of Extended Gamma Ray Emission towards the Galactic Center

We construct empirical models of the diffuse gamma-ray background towards the Galactic Center. Including all known point sources and a template of emission associated with interactions of cosmic rays with molecular gas, we show that the extended emission observed by the Fermi Gamma Ray Telescope toward the Galactic Center is detected at high significance for all permutations of the diffuse model components. However, we find that the spectra of the sources in our model change significantly with the inclusion of new background models. We discuss implications for the central Sgr A* source as well as dark matter annihilation. If the extended emission is interpreted to be astrophysical in origin, we obtain strong bounds on dark matter annihilation, although systematic uncertainties due to the dependence on the background models are significant.

Speaker: Dr Shunsaku Horiuchi (UC Irvine)

Slides 3.horiuchi_PONT.pdf

3:40 PM Internal bremsstrahlung signatures of Dark Matter annihilations in light of direct detection and collider searches

If dark matter annihilates into light fermions mediated by colored or charged scalar particles, the effect of internal bremsstrahlung yields a sharp spectral feature in the gamma spectrum. This line-like feature could be detetcted in the cosmic gamma-ray flux by current and future observatories, while being in agreement with constraints from secondary gamma-rays and antiprotons. We discuss complementary constraints on this class of models from direct detection and collider searches, and the interplay of future indirect and direct searches like CTA and Xenon1T

Speaker: Mathias Garny (CERN)

Slides talk.pdf

4:00 PM Recent results from the LUX dark matter search

We will present recent results from the LUX experiment, including the first dark matter search results made public in November 2013, as well as the results of additional studies of relevance to the field.

Speaker: Simon Fiorucci (Brown University)

Slides 20140415_Fiorucci_LUX.pdf

4:20 PM Coffee Break

4:50 PM Indirect Search for Dark Matter with the ANTARES Neutrino Telescope

The ANTARES Collaboration is operating the largest water Cherenkov neutrino telescope in the Northern hemisphere, installed in the Mediterranean Sea offshore France. One major goal of ANTARES is the search for neutrinos produced in self-annihilation of Dark Matter particles, for instance in the direction of the Sun or the Galactic Centre. The results on the search for Dark Matter annihilations in the Sun with the data recorded between 2007 and 2012 are presented. The obtained competitive limts on the WIMP-proton cross-section are compared to the ones of other indirect and direct detection experiments as well as to predictions of SUSY models such as CMSSM and MSSM-7 models. New preliminary results of ANTARES on Dark Matter searches towards the Galactic Centre are also presented, leading to the most stringent limits on the annihilation cross-sections for high mass WIMPs. Finnaly, preliminary sensitivities on indirect search towards dwarf galaxies and the centre of the Earth are also expected to be presented.

Speaker: Vincent Bertin (Centre National de la Recherche Scientifique (FR))

Slides Bertin-DM_Antares-PONT14.pdf Bertin-DM_Antares-PONT14.pptx

5:10 PM Probing Nu-Forces at IceCube

The IceCube experiment has recently detected the highest-energy neutrino events yet recorded. This data is remarkable both for the significant excess of neutrino events above known backgrounds, and also for the conspicuous lack of events both above and below 1 PeV. I’ll discuss a simple model of neutrino self-interactions mediated by a MeV-scale boson that can account for these peculiar features of the IceCube spectrum. If this mediator also interacts with dark matter, it can alleviate long-standing tension with the observed abundances and internal structure of dwarf galaxies.

Speaker: Ian Shoemaker (Los Alamos)

Slides 7.Shoemaker_Pont_NuForces.key

5:30 PM Anti-nuclei from Dark Matter

Light anti-nuclei, namely anti-deuteron and anti-helium, can be produced through the nuclear coalescence of the anti-protons and the anti-neutrons that are originated in a dark matter pair annihilation event. At low kinetic energies, the fluxes of these bound states are found to dominate over the astrophysical background and thus anti-nuclei may be considered as a very promising channel for a dark matter indirect detection, especially for WIMPs with a low or intermediate mass. In this talk, an overview on the principal issues related both to the anti-nuclei production and to their subsequent propagation through the interstellar medium and the heliosphere will be given. Then, the capability of current and future experiments to detect a light anti-nuclei flux produced by dark matter annihilation will be investigated in relation to the constraints on the dark matter annihilation cross section that can be derived from the latest measurements of the cosmic anti-proton flux.

Speaker: Andrea Vittino (Universita' di Torino and IPhT/CEA Saclay)

Slides Vittino_Anti_nuclei_from_DM.key

5:50 PM Search for Ultra-high energy neutrinos at the Pierre Auger Observatory:

Neutrinos in the sub-EeV energy range and above can be detected with the Surface Detector array (SD) of the Pierre Auger Observatory. They can be identified through the broad time-structure of the signals expected to be induced in the SD stations. The identification can be done for neutrinos of all flavours interacting in the atmosphere at large zenith angles, in the ranges 60-75 deg and 75-90 deg (downward-going), as well as for Earth-skimming neutrino interactions in the case of tau neutrinos (upward-going). The three different searches have been performed in the data from 1 January 2004 up to 31 December 2012. The results have been combined, providing, in the absence of candidates, an updated and stringent limit to the diffuse flux of ultra-high energy neutrinos.

Speaker: Francesco Salamida (Institut de Physique Nucléaire d'Orsay)

Slides SalamidaPONTAvignon.pdf

6:10 PM Higher order dark matter annihilations in the Sun and implications for IceCube

Dark matter particles that have been captured inside the Sun can annihilate producing high-energy neutrinos which would be a smoking-gun signal if observed in terrestrial neutrino detectors such as IceCube. Annihilation channels like $e^+e^-$ or $\mu^+ \mu^-$, or $q \bar{q}$ however, only produce neutrinos in the MeV range due to the interaction of the annihilation products with the solar material and were consequently partly neglected in the literature. Still, the interaction mediating these annihilation processes necessarily produces gauge bosons by higher order effects, which in turn produce highly energetic neutrinos. We consider the annihilation into a fermion-antifermion pair in a model-independent contact interaction approach. Concretely, we investigate the annihilation into $f \bar{f}$ and associated emission of one gauge boson as well as annihilations into two gauge bosons at the one-loop level in order to calculate limits on the scattering cross section of dark matter and protons from the non-observation of an excess of events in IceCube. We show that the limits on the spin-dependent cross section are, for some annihilation channels, stronger than those reported by COUPP and SIMPLE. Furthermore, we give an example of a simple Particle Physics model to which the model-independent techniques can be mapped.

Speaker: Maximilian Totzauer (Technische Universität München)

Slides PONTAvignon2014_MTotzauer.pdf

6:20 PM Dark matter annihilations and decays after the AMS-02 positron measurements

We use the new positron data from the AMS-02 experiment to set limits on dark matter annihilations and decays in different channels. In this work it is assumed that the positron background consists of secondary positrons from spallations and an additional primary component of astrophysical origin. We show that the positron flux and the positron fraction give competitive limits on the dark matter properties. Concretely, we can exclude the thermal cross section for dark matter masses below 100 GeV in the electron channel and for masses below 60 GeV in the muon channel.

Speaker: Anna Lamperstorfer (TUM)

Slides talk_lamperstorfer-PONT.pdf

Wednesday, April 16

9:00 AM → 12:30 PM 4-Dark Matter

9:00 AM Indirect detection of dark matter

I will present status and some perspectives on indirect detection of particle dark matter.

Speaker: Jan Conrad (Stockholm University)

Slides Avignon_April_2014.pdf

9:45 AM A Brief Overview of Direct Searches for Dark Matter

Direct detection experiments seek to detect dark matter though its scattering off nuclei in terrestrial detectors. In this talk, I will review the motivation for the direct detection of dark matter, discuss a variety of challenges faced by experimenters trying to directly detect dark matter and review recent results from leading direct detection experiments.

Speaker: Jodi Cooley (SMU)

Slides cooley_pont2014.pdf

10:30 AM Coffee Break

11:00 AM Clues to the identity of the dark matter from simulations and observations

Speaker: Carlos Frenk

Slides frenk.pdf

11:45 AM A WIMP dark matter particle around the corner?

This is a new title for my talk to replace the previous title.

Speaker: Thomas Hambye

Slides DMAvignon2014Hambye.pdf

12:30 PM → 2:30 PM Lunch Break

2:30 PM → 6:30 PM Afternoon session

2:30 PM Non-local gravity and dark energy

We discuss recent work on non-local modifications of gravity obtained adding a term $m^2 R\Box^{-2}R$ to the Einstein-Hilbert action. We find that, despite the presence of a mass parameter, the resulting theory has no ghost, no vDVZ discontinuity, and no no Vainshtein radius below which the theory becomes strongly coupled. For $m$ of order $H_0$ the theory therefore recovers all successes of GR at solar system and lab scales, and only deviates from it at cosmological scales. We examine the cosmological consequences of the model and we find that it automatically generates a dynamical dark energy and a self-accelerating evolution. After fixing our only free parameter $m$ so to reproduce the observed value of the dark energy density today, we get a pure prediction for the dark energy equation of state, $w_ {\rm DE}\simeq-1.14$. This value is in excellent agreement with the Planck result $w_{\rm DE}=-1.13^{+0.13}_{-0.14}$ and would also resolve the existing tension between the Planck data and local measurements of the Hubble parameter.

Speaker: Michele Maggiore (University of Geneva)

Slides avignon.pdf

3:00 PM Dark Energy phenomenology: the effective field theory approach

The discovery of the accelerating expansion of the Universe is motivating an impressive amount of theoretical and observational activity. I will focus on recent and ongoing works that aim at a unifying description of dark energy and modified gravity models containing a scalar degree of freedom in addition to general relativity. Such an effective field theory approach allows, on the one hand, a transparent analysis of the possible theoretical mechanisms at the basis of dark energy; moreover, it provides a useful set of parameters that can be efficiently constrained with observations. I will show the present observational constraints based on the growth rate of cosmic structures and the forecasts for future surveys such as EUCLID.

Speaker: Dr Federico Piazza (APC)

Slides Avignon.pdf

3:30 PM On the non-linear scale of cosmological perturbation theory

I discuss the use of perturbative methods to study the evolution of matter fluctuations in the context of large scale structure formation. After an short introduction, I compare several techniques in perturbation theory as renormalized perturbation theory, the eikonal approximation and Pade resummation.

Speaker: Thomas Konstandin (DESY, Hamburg)

Slides sem_Avignon.pdf

4:00 PM Large-scale structures in some modified-gravity scenarios

We study the effects of screened modified gravity of the $f(R)$, dilaton and symmetron types on structure formation, from the quasi-linear to the non-linear regime, using semi-analytical methods. For such models, where the range of the new scalar field is typically within the Mpc range and below in the cosmological context, non-linear techniques are required to understand the deviations of the power spectrum of the matter density contrast compared to the $\Lambda$-CDM template. This is nowadays commonly tackled using extensive N-body simulations. Here we present results combining exact perturbation theory at the one loop level (and a partial resummation of the perturbative series) with a halo model.

Speaker: Patrick Valageas (CEA)

Slides valag1.pdf

4:20 PM Coffee Break

4:50 PM Cosmological constraints on Lorentz Invariance of the Universe

Lorentz Invariance is believed to be a fundamental property of Nature. However, recently this assertion has come under scrutiny, which is motivated on one hand by the Lorentz-violating proposals for quantum gravity and on the other hand, by the fact that Lorentz Invariance has been tested with ultimately high precision only in the sector of Standard Model of particles. For other sectors the bounds are milder or even non-existent. My talk will be devoted to the question how cosmological data can be used to test Lorentz Invariance in gravity and dark matter. I will focus on the case, where Lorentz Invariance is violated by a preferred frame, parametrized by a unit time-like vector $u^{\mu}$ described within Einstein-aether and khronometric gravity theories. I will describe how this preferred frame and its possible coupling to dark matter particles affect the homogeneous expansion of the Universe and the behaviour of cosmological perturbations. Finally, I will present the most stringent results to date on constrains for the departures from Lorentz Invariance in the dark matter and gravity sectors, based on current cosmological data.

Speaker: Mikhail Ivanov (Moscow State University)

Slides avignon_Ivanov.pdf

5:10 PM Dark D-brane Cosmology

The talk is about the possibility of matter residing on a brane moving in extra dimensions. Such matter would be disformally coupled to gravity. Due to a screening mechanism, the coupling could be viable even in the visible sector. The Dirac-Born-Infeld set-up in type II string theory is used to illustrate how the coupling functions can be explicitly deduced from the higher dimensional geometry, and general implications of disformal matter couplings are reviewed. A concrete cosmological model with dark matter residing on the moving brane is presented to demonstrate how some fine-tuning problems of the dark sector might be alleviated in this framework.

Speaker: Tomi Koivisto (Nordita)

Slides PONT2014.pdf

5:30 PM Consistency relations for large scale structure

Consistency relations for large scale structure are relations between an n-point and an (n+1)-point correlation function of the matter or galaxy distribution, in the limit in which one of the momenta is much smaller than the others. I will show that these relations are non perturbative in the small modes. Moreover, since they are consequence of the Equivalence Principle, their violation can be used to probe the presence of extra forces in the universe, using the next generation of galaxy surveys.

Speaker: Jérôme GLEYZES

Slides Gleyzes.PONT.pdf

5:40 PM Backreaction in Swiss Cheese models

Inhomogeneous cosmological models are often constructed using the Swiss Cheese scheme. I will show that under certain physical assumptions, backreaction must always be small in these models. However, it is possible to break one of these conditions to construct a consistent (but un-physical) solution where backreaction can be large. Finally I will discuss how supernova observations would be interpreted in such a universe.

Speaker: Mikko Lavinto (University of Helsinki)

Slides lavinto_PONT.pdf

5:50 PM Beyond single stream with the Schrödinger method

We investigate large scale structure formation of collisionless dark matter in the phase-space description based on the Vlasov (or collisionless Boltzmann) equation whose nonlinearity is induced solely by gravitational interaction according to the Poisson equation. Determining the time-evolution of density and peculiar velocity demands solving the full Vlasov hierarchy for the moments of the phase-space distribution function. In the presence of long-range interaction no consistent truncation of the hierarchy is known apart from the pressureless fluid (dust) model which is incapable of describing virialization due to the occurrence of shell-crossing singularities and the inability to generate higher cumulants like vorticity and velocity dispersion. Our goal is to find a phase-space distribution function that is able to describe regions of multi-streaming and therefore can serve as theoretical N-body double. We use the coarse-grained Wigner probability distribution obtained from a wavefunction fulfilling the Schrödinger equation and show that its evolution equation bears strong resemblance to the Vlasov equation but cures the shell-crossing singularities. This feature was already employed in cosmological simulations of large-scale structure formation by Widrow & Kaiser (1993). The coarse-grained Wigner ansatz allows to calculate all higher moments from density and velocity analytically thereby incorporating nonzero higher cumulants in a self-consistent manner. On this basis we are able to show that the Schrödinger method automatically closes the corresponding hierarchy such that it suffices to solve a Schrödinger equation in order to determine density and velocity and thereby all higher cumulants.

Speaker: Mrs Cora Uhlemann (Arnold Sommerfeld Center for Theoretical Physics, LMU)

Slides CUSchrödingerVlasovAvignon.pdf

6:00 PM Probing non-standard gravity with the growth index of cosmologicl perturbations

The growth index of cosmological perturbations is one of the most powerful probes of the nature of Dark Energy (DE), the mysterious mechanism driving the late epoch acceleration of the universe. Unlike classical geometrical observables, such as distances, which only probe the background sector of a cosmological model, this observable provides insight into first order dynamical effects, and it is therefore a key test for modified gravity scenarios often invoked to explain away the DE issue. In this talk I will first show how the whole information about the growth rate history of linear cosmic structures can be precisely encoded into a small set of growth index parameters whose amplitude can be analytically predicted by theory. Then I will go on demonstrating how these parameters naturally define a space where theoretical predictions can be compared against data in a model independent way. Finally, by exploiting the Effective Field Theory of dark energy, a formalism which describes virtually all the gravitational theories containing a single scalar degree of freedom in addition to the metric, I will explore which alternative cosmological scenarios are not in conflict with current growth data.

Speaker: Mr Heinrich Steigerwald (Aix-Marseille University / Centre de Physique Théorique)

Slides 2014-04-15_Heinrich_GrowthIndex.pdf

6:10 PM Probing the power spectrum of matter with the galaxy clustering ratio

The galaxy clustering ratio (Bel & Marinoni 2014 A&A, 563, 36, Bel et al. 2014 A&A 563, 37) is a new clustering statistic that provides access to characteristic parameters of the power spectrum of mass density fluctuations without the need to specify the galaxy biasing function nor a model for peculiar velocity distortions. I will demonstrate the method using galaxy simulations as well as real redshift data (from the VIPERS and the SDSS surveys) and show that it allows to fix the reduced density of matter to a precision of nearly 6%. I will argue that this approach will be instrumental in searching for evidences of new physics beyond the standard model of cosmology and in planning future redshift surveys such as EUCLID.

Speaker: Julien Bel (Osservatorio Astronomico di Brera)

Slides pont_bel.pdf

6:20 PM A new approach to chameleon theories

Most theories that predict time and/or space variation of fundamental constants also predict violations of the Weak Equivalence Principle (WEP). Khoury and Weltmann proposed the chameleon model in 2004 and claimed that this model avoids experimental bounds on WEP. Mota and Shaw analized the non-linear regime and concluded that only this case predicts no violations of the WEP while the linear and cuasilinear regimes do. We present a contrasting view based on a new calculation of the the two body problem for the chameleon field and show how the force depends on the test body composition.

Speaker: Dr Lucila Kraiselburd (Facultad de Ciencias Astronomicas y Geofisicas-Universidad Nacional de La Plata, Argentina)

Slides LKrai16042014.pdf

Thursday, April 17

9:00 AM → 12:30 PM 5-Gravity and modified gravity

9:00 AM Massive gravity and cosmology

The search for a consistent theory of finite-range gravity is a longstanding problem and well motivated by both theoretical and observational considerations. On the theoretical side, whether there exists such a consistent extension of general relativity by a mass term is a basic question of classical field theory. After Fierz and Pauli's pioneering attempt in 1939, this issue has been attracting a great deal of interest. On the observational side, continuing experimental probes of gravity have revealed new unexpected phenomena at large scales. One of the most profound discovery is the cosmic acceleration, which was found in 1998. The extremely tiny energy-scale associated with the cosmic acceleration hints that gravity might need to be modified in the infrared. The massive gravity is one of the most interesting attempts in this direction. In this talk, after reviewing the history and recent developments of massive gravity, I will describe cosmological solutions and their stability.

Speaker: Shinji Mukohyama (Kavli IPMU, U of Tokyo)

Slides 140417mukohyama.pdf

9:45 AM Testing General Relativity with Cosmology

With the successes of observational cosmology, a new window has opened up on to gravitational physics. By carefuly measuring the morphology and growth of structure in the Universe it may be possible to constrain general relativity on a completely new range of scales. It also allows us to explore a plethora of modified gravity theories that have emerged as an attempt to explain the observational evidence for dark energy. I will discuss the challenges and approaches which are being taken in this new field.

Speaker: Prof. Pedro G. Ferreira (University of Oxford)

Slides 2.Ferreira_Avignon_2014.pdf

10:30 AM Coffee Break

11:00 AM Modified Gravity at Crossroad

I will review some of the recent progress and current status in the studies of two important modified gravity theories to explain the cosmic acceleration: Galileon gravity and f(R) gravity. I will discuss possible cosmological, astrophysical or terrestrial constraints on these, and other related, theories for the near future. Based on these, I will promote Galileon gravity as a competitive alternative to LCDM and explain why it merits further studies from the wider community.

Speaker: Dr Baojiu Li (Institute for Computational Cosmology, Durham University)

Slides Avignon-Apr-2014-Li.pdf

11:45 AM Gravitational wave standard sirens and cosmology

Inspiralling binaries of neutron stars and black holes are self-calibrating standard sirens whose observations can measure the luminosity distance without the need to make any complicated modelling of the sources. For binary neutron stars it is also possible to measure the source redshift from gravitational-wave observations alone. Together with joint observations of sources in both the gravitational-wave and electromagnetic windows it should be possible to obtain source catalogues with measured values of luminosity distances and redshifts. In this talk I will discuss how such catalogues could be used for cosmography.

Speaker: Bangalore Sathyaprakash (Cardiff University)

Slides 140414-GW-Cosmology.key 140414-GW-Cosmology.pdf

12:30 PM → 2:30 PM Lunch Break

2:30 PM → 6:30 PM Afternoon session

2:30 PM Massive black holes and galaxy formation: state of the art and implications in cosmology

Massive black holes, weighing millions to billions of solar masses, inhabit the centers of today's galaxies. The progenitors of these black holes powered luminous quasars within the first billion years of the Universe. The first massive black holes must therefore have formed around the time the first stars and galaxies appeared and then evolved along with their hosts for the past thirteen billion years. I will discuss some aspects of the cosmic evolution of massive black holes, from their formation to their growth and the interplay between black holes and galaxies.

Speaker: marta volonteri

Slides PONTAvignonMVolonteri.pptx

3:00 PM Supermassive black holes, gravitational waves and cosmology

Within this decade the detection of gravitational waves (GWs) may be a reality, opening a completely new window on the Universe. The low frequency window will be dominated by signals emitted by a cosmological population of massive black hole binaries (MBHBs). I will review several aspect of MBH physics, including their formation, evolution, interaction with their environment and gravitational wave (GW) emission. I will pay particular attention to the prospect of GW detection with pulsar timing arrays and/or future space based interferometers and on the astrophysical and cosmological information that such detection will carry.

Speaker: Dr Alberto Sesana (Albert Einstein Institute)

Slides Sesana_Avignon14.pdf

3:30 PM Cosmology with the 21 cm line

Three-dimensional mapping of neutral hydrogen gas at the high redshift using the redshifted 21 cm line has recently emerged as a promising cosmological probe. I will discuss the prospects for constraining cosmological parameters, including those beyond the standard LCDM model, using the 21 cm line.

Speaker: Yi Mao (Institut d'Astrophysique de Paris)

Slides Yi_MAO_21cm_cosmology.ppt

4:00 PM Measuring relativistic effects with anti-symmetric galaxy correlations

In the past few years it has been shown that the two-point correlation function of galaxies is affected by relativistic effects at large scales. Various terms like gravitational redshift, Doppler effects or time delay corrections induce subtle changes in the correlation function. These effects are however subdominant at all but the largest scales, rendering their detection challenging. In this talk, I will present a novel method to measure relativistic effects in large-scale structure by looking at the anti-symmetric part of the correlation function between two populations of galaxies. I will show that gravitational redshift and Doppler terms induce a dipolar modulation in the correlation function, which allows to isolate the relativistic effects at scales accessible by current surveys.

Speaker: Camille Bonvin (University of Cambridge)

Slides relativistic.pdf

4:20 PM Coffee Break

4:50 PM Dark Energy Survey: Status Report and Early Cluster Science

The Dark Energy Survey (DES) is in the early phases of a five-year project to survey 5000 sq degrees of sky to ~24th mag in 5 optical bands and employ the data to test cosmic acceleration using weak lensing, supernovae, galaxy clustering and clusters of galaxies. I will present a status summary of DES and provide some examples of early science, particularly focused on clusters of galaxies.

Speaker: August Evrard (University of Michigan)

Slides evrard_DESclusters.key

5:10 PM Cosmic variance on the local expansion rate.

The local expansion rate as observed by for example the HST, is not the same as the global expansion rate in the FLRW metric. In a standard LCDM universe, the effect of local dynamics on the apparent expansion rate turns out to be significant, especially compared to the tight error bars in today's precision cosmology. I show how the linear power spectrum of perturbations gives a straightforward prediction on the variance of the gravitational potential of the observer, which in turn leads to a variance in the expansion rate that the observer sees. This effect alleviates half of the discrepancy between the expansions rates as interpreted from the Planck satellite data and from astrophysical sources such as Cepheids and Supernovae.

Speaker: Wessel Valkenburg (Leiden University)

Slides valkenburgPONT.pdf

5:30 PM Cosmology with photometric quasars

Quasars are highly biased tracers of the large-scale structure and therefore powerful probes of the initial conditions and the evolution of the universe. However, current spectroscopic catalogues are too small for studying the clustering of quasars on large-scales and over extended redshift ranges. Hence one must resort to photometric catalogues, which include large numbers of quasars identified using imaging data but suffer from significant stellar contamination and systematic uncertainties. We will present a detailed analysis of the clustering of photometric quasars from the Sloan Digital Sky Survey, and demonstrate that the effects of observational systematics can be robustly eliminated with appropriate techniques. In particular, we will show how to mitigate the impact of spatially varying systematics, such as calibration and observing conditions, using an extended mode projection approach when correlating the quasar samples. We will finally present constraints on the quasar bias in the range $0.5 < z < 3.5$ derived using an optimal estimator that exploits both the clustering of the quasar samples and their cross-correlation with CMB lensing.

Speaker: Mr Boris Leistedt (University College London)

Slides leistedt_pont_avignon.pdf

5:50 PM Probing beyond standard model physics via Hawking radiated gravitational waves

We propose a novel technique to probe the high energy physics beyond the standard model (BSM). By observing gravitational waves emitted by the Hawking radiation of black holes, we can scan the unknown high energy physics for the following reasons. (i) A particles is emitted by black holes only if its mass is smaller than the Hawking temperature $T_{BH}$ of a black hole. (ii) Since a black hole starts radiating BSM particles when $T_{BH}$ reaches the BSM mass scale, the time evolution of $T_{BH}$ is sensitive to the mass spectrum of the high enertgy physics. (iii) Although gravitons are not directly affected by the emissions of BSM particles, their radiation depends on the evolution of $T_{BH}$. Therefore the information of the BSM theory (including a dark sector) is imprinted in the gravitational wave spectrum $\Omega_{GW}(\nu)$ produced by light black holes. As an interesting exmaple, we calculate $\Omega_{GW}(\nu)$ generated by primordial black holes which are light enough to evaporate in the early universe and explore how the degrees of freedom in BSM theory distort the spectrum $\Omega_{GW}(\nu)$.

Speaker: Mr Tomohiro Fujita (Kavli IPMU, Tokyo University)

Slides Fujita_slide.pdf

7:30 PM → 10:30 PM Banquet

Friday, April 18

9:00 AM → 12:30 PM 3-Observational Cosmology

9:00 AM Cosmology with type-Ia Supernovae

The large-scale search for type Ia supernovae, which has been undertaken since the discovery of the accelerated expansion of the universe in the late nineties, has been largely successful. With now about 1000 SNe-Ia on the Hubble diagram, recent type Ia supernovae surveys provide a precise mapping of the distance-redshift relation up to $z\sim1$, setting, at this time,the most stringent constraint on the nature of dark energy. In this contribution, we review the status of cosmology with SNe Ia. We present the available sample and discuss systematic uncertainties affecting the measurement. We present recent improvements on this topic and the associated improvement on cosmological constraints. We then discuss improvement perspectives and the future of the probe.

Speaker: Marc Betoule

Slides 1.betoule_avignon_2014.pdf

9:45 AM Cosmology with the Euclid satellite

I will review the Euclid satellite mission and forecasts for cosmological implications.

Speaker: Valeria Pettorino (U)

10:30 AM Coffee Break

11:00 AM LSS and BAO: current status and prospects

The Baryon Acoustic Oscillation (BAO) standard ruler has risen in prominence over the last decade, reaching a 1% distance measure at z = 0.57 with the latest release from the SDSS-III BOSS survey and providing the first detection of the BAO in the Lyman-alpha forest. The same large scale structure (LSS) surveys allow constraints on the growth rate of cosmic structure through redshift space distortions. I will review the current status of both measurements and their cosmological implications. Upcoming spectroscopic surveys like Euclid and DESI will vastly expand the redshift coverage and precision. They should have sufficient sensitivity to detect massive neutrinos even at the minimal mass allowed by oscillation experiments.

Speaker: Dr Beth Reid (UC Berkeley)

Slides 3.PONTAvignon_Reid.pdf

11:45 AM Cosmic Acceleration Then and Now

Speaker: Josh Frieman (Fermilab)

Slides 4.Frieman-Avignon.pdf 4.Frieman-Avignon.pptx

12:30 PM → 2:30 PM Last Lunch