Progress on Old and New Themes in cosmology (PONT) 2011

18 Apr 2011, 08:00 → 22 Apr 2011, 13:00 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.

Organizers:  
   Philippe Brax (CEA IPhT Saclay)
   Chiara Caprini (CNRS IPhT Saclay)
   Marco Cirelli (CERN-TH & CNRS IPhT Saclay)
   Géraldine Servant (CERN-TH & CEA IPhT Saclay)

Monday 18 April

Early Universe

1 Inflation

Speaker: leonardo senatore (stanford university)

Slides senatore_seminar_Avignon_April_2011_2_export.pdf

2 (P)Re-heating

Speaker: Neil Barnaby

movie RoulettePreheat.wmv

Slides avignon.pdf

10:30 Coffee Break

3 Inflation and strings

Speaker: Alexander Westphal (DESY Hamburg)

movie of slides 3.Westphal.mov

Slides 3.Westphal.pdf

4 The EW scale in cosmology

Speaker: Mikhail Shaposhnikov

Slides 4.Shaposhnikov.pdf

12:30 Lunch Break

Contributed Talks

5 Nonstandard tensor modes from a pseudoscalar inflaton

In many models of inflation, the inflaton is a pseudoscalar field that is a potential source of parity violation. I will discuss a natural mechanism allowing to transfer parity violation from the inflaton into the Cosmic Microwave Background (CMB). A pseudoscalar inflaton naturally interacts with gauge fields through an axion-like coupling. Through this coupling, the rolling inflaton induces the production of quanta of the gauge field, that in their turn source the tensor components of the metric perturbations. Due to the parity-violating nature of the system, non-vanishing TB and EB correlation functions in the CMB are generated. I will also discuss how the tensor modes generated this way might be directly detected by gravitational wave interferometers such as advanced LIGO.

Speaker: Lorenzo Sorbo (University of Massachusetts, Amherst)

Slides Sorbo_PONT11.pdf

6 Gauge Non-Singlet Matter Inflation in Supergravity

We discuss a novel class of inflation models in supergravity with gauge non-singlet matter fields as the inflaton. It is based on a ‘tribrid’ structure in the superpotential and on a ‘Heisenberg symmetry’ for solving the η-problem. Inflation ends via a waterfall phase transition, as in hybrid inflation. In the context of grand unified theories, the unified matter superparticle provides a promising inflaton candidate. We also comment on how a generalization of this model class may be suitable for realising inflation in heterotic orbifold compactifications, where the Heisenberg symmetry is a property of the tree-level Kahler potential of untwisted matter fields.

Speaker: Dr Stefan Antusch (MPI of Physics, Munich)

Slides Pont2011_Antusch.pdf Pont2011_Antusch.ppt

7 Cosmological perturbations in the UV-protected inflation

In natural inflation, the inflaton is a pseudo-Nambu-Goldstone boson which acquires a mass by explicit breaking of a global symmerty at scale f. In this case, for small field values, the potential is flat and stable under radiative corrections. However, slow roll conditions enforce f much larger than M_pl making the validity of the whole scenario questionable. In this talk, we show that a coupling of the inflaton kinetic term to the Einstein tensor allows f much smaller than M_pl by enhancing the gravitational friction acting on the inflaton during inflation. This new interaction, keeps the theory perturbative in the whole inflationary trajectory, preserves the tree-level shift invariance of the pseudo-Nambu-Goldstone Boson and avoids the introduction of any new degrees of freedom with respect to the standard natural inflation. We also study the nonlinear cosmological perturbations in this model. We estimate the non-Gaussianity and show that the local-type non-Gaussianity satisfies the single-field consistency relation.

Speaker: Dr Yuki Watanabe (LMU Munich)

Slides watanabe_pont_apr2011.pdf

8 Can thermal masses constrain the reheating temperature?

It has been suggested that large thermal masses of the decay products can close the phase space for inflaton decay. This can impose an upper bound on the reheating temperature which does not depend on the inflaton coupling. We study the problem from first principles of nonequilibrium quantum field theory and discuss under which conditions this intuitive argument, based on the kinematics of classical particles, can be applied in the dense primordial plasma.

Speaker: Dr Marco Drewes (Ecole Polytechnique Federale de Lausanne (EPFL))

Slides PONT.pdf

9 Imperfect Dark Energy of Kinetic Gravity Braiding

In this talk I will discuss a new class of cosmological scalar fields. Similarly to gravity, these theories are described by actions linearly depending on second derivatives. The latter can not be excluded without breaking the generally covariant formulation of the action principle. Despite the presence of these second derivatives the equations of motion are of the second order. Hence there are no new pathological degrees of freedom. Because of this structure of the theory the scalar field kinetically mixes with the metric- the phenomenon we have called Kinetic Gravity Braiding. These theories have rather unusual cosmological dynamics which may be useful to model Dark Energy and Inflation. I will discuss an equivalent hydrodynamical formulation of these theories, stability and causality for the fluid like configurations and cosmological applications.

Speaker: Alexander Vikman (CERN)

Slides 5.Vikman.pdf PONT_Avignon.key

10 Minimal models of inflation -- connecting cosmology and experiment

Current Standard Model of elementary particles nicely describes (nearly) all phenomena observed in the laboratories. On cosmological scales the situation is much worse -- reliable experimental observations do not fit into the Standard Model. In the beginning the Universe had a period of inflationary expansion, now it is filled with Dark Matter and has baryon asymmetry. All these require explanation beyond the Standard Model. I will argue on the examples of the model with light inflaton and of Higgs inflation that extending the SM in a very minimal way leads to explanation of all these experimental facts, and connects Universe behaviour at the earliest (inflationary) stage to the possible effects in modern laboratories.

Speaker: Dr Fedor Bezrukov (LMU)

Slides talkPONT2011.pdf

16:30 Coffee Break

Contributed Talks

11 Unitarizing Higgs inflation

We consider a simple extension of the Standard Model Higgs inflation with one new real scalar field which preserves unitarity up to the Planck scale. The new scalar field (called sigma) completes in the ultraviolet the theory of Higgs inflation by linearizing the Higgs kinetic term in the Einstein frame, just as the non-linear sigma model is unitarized into its linear version. The unitarity cutoff of the effective theory, obtained by integrating out the sigma field, varies with the background value of the Higgs field. In our setup, both the Higgs field and the sigma field participate in the inflationary dynamics, following the flat direction of the potential. We obtain the same slow-roll parameters and spectral index as in the original Higgs inflation but we find that the Hubble rate during inflation depends not only on the Higgs self-coupling, but also on the unknown couplings of the sigma field.

Speaker: Dr Hyun Min Lee (CERN)

Slides avignon2011_hmlee.pdf

12 Galilean symmetry in the EFT of inflation: new shapes of non-Gaussianity

We study the consequences of imposing an approximate Galilean symmetry on the Effective Theory of Inflation, the theory of small perturbations around the inflationary background. This approach allows us to study the effect of operators with two derivatives on each field, which can be the leading interactions due to non-renormalization properties of the Galilean Lagrangian. In this case cubic non-Gaussianities are given by three independent operators, containing up to six derivatives, two with a shape close to equilateral and one peaking on flattened isosceles triangles. The four-point function is larger than in models with small speed of sound and potentially observable with the Planck satellite.

Speaker: Dr Guido D'Amico (NYU)

Slides galeft_avignon.pdf

13 Primordial fluctuations and non-Gaussianities in a Galilean theory

We consider a multi-scalar-tensor model of gravity in which the action contains higher-order derivatives of the scalar fields without introducing extra propagating degrees of freedom. In the context of an inflationary era, we study the background evolution of this model as well as the linear and non-linear properties of the cosmological fluctuations it generates. Orthogonal non-Gaussianities are shown to arise for the first time in a concrete model and new shapes of non-Gaussianities are identified.

Speaker: Dr Sebastien Renaux-Petel (University of Cambridge)

Slides 9.Renaux-Petel.pdf

14 Inflection point inflation with MSSM Higgs fields

We demonstrate that in the simplest CP conserving scenario, the MSSM higgs fields can act as an inflaton, in the presence of a Planck suppressed non-renormalizable term in the superpotential. The inflation occurs around an inflection point which can match the current WMAP data. Since inflation occurs at a low scale, the moduli problem does not appear, and the supergravity corrections remain negligible. However, there is a fine tuning needed between the MSSM paramaters involved, at a high energy scale. We use the Suspect RGE code to show that, however, successful EWSB is possible over a large parameter space in spite of the fine tuning at a high scale, and also that the fine tuning at a high scale does not correspond to any fine tuning at the EWSB scale.

Speaker: Mr Arindam Chatterjee (University of Bonn)

Slides 10.Chatterjee.pdf

15 Supercurvaton

I discuss the curvaton scenario implemented in the context of the simplest model of chaotic inflation in supergravity. I investigate observational consequences and theoretical features of this model. The non-Gaussianity parameter f_{NL} in this scenario can be either very small or very large, and it can take different values in different parts of the universe. Under certain conditions, this parameter can take values in the observationally interesting range from O(10) to O(100). This investigation makes a close connection between the fundamental theory of supergravity and the observational measurements.

Speaker: Vittoria Demozzi (LMU Munich)

Slides Demozzi_Pont2011.pdf

16 Vector fields and Loop Quantum Cosmology

In the context of the Loop Quantum Cosmology we have analysed the holonomy correction to the classical evolution of the simplified Bianchi I model in the presence of vector fields. For the Universe dominated by a massive vector field or by a combination of a scalar field and a vector field a smooth transition between Kasner-like solution and expanding Bianchi I Universe has been demonstrated. In this case a lack of initial singularity and a finite maximal energy density appear already at the level of General Relativity, which simulates a classical Big Bounce.

Speaker: Mr Michal Artymowski (IFT, University of Warsaw)

Slides Artymowski_Avignon_2011.pdf

19:00 Welcome cocktail

Tuesday 19 April

Astroparticle

17 Hot relics: which ones, how many, and how to know more

Speaker: Yvonne Wong

Slides yyyw.pdf

18 Constraints on magnetic fields

Speaker: Ruth Durrer (University of Geneva)

Slides 2.Durrer.pdf

10:30 Coffee Break

19 Recent developments in baryo/lepto-genesis

Speaker: Michael Ramsey-Musolf (U. Wisconsin-Madison)

Slides MRMAvignon11.pdf

20 Gravitational Waves astronomy

Speaker: Alberto Vecchio (Birmingham)

Slides 4.Vecchio.pdf

12:30 Lunch Break

Contributed Talks

21 Supersonic Electroweak Baryogenesis: Achieving Baryogenesis from Fast Bubble Walls

It is widely assumed that for the Electroweak Baryogenesis mechanism to be effective in generating the baryon asymmetry of the Universe, the first order phase transition bubbles have to expand at a subsonic speed (in order to allow for the diffusion of CP asymmetric currents in front of the wall). Here we present a new mechanism for Electroweak Baryogenesis that is effective for supersonic bubble walls, and relies on the formation of small bubbles of symmetric phase in the plasma behind the bubble wall (which is in the broken phase) due to the heating of the plasma as the wall passes by.

Speaker: Dr Jose Miguel No (IPhT CEA Saclay)

Slides PontAvignon2011.pdf

22 Electroweak Baryogenesis from a Composite Higgs Sector

One of the most appealing explanation of physics at the electroweak scale is given by composite Higgs models, where the Higgs boson is a bound state of a new strongly-interacting dynamics. While the minimal realization of compositeness differs only slightly from the Standard Model (SM), non-minimal realizations, based on larger coset structures, can have a much richer phenomenology and account for phenomena that can't be explained within the SM, such as electroweak baryogenesis (EWBG). In particular, in models based on the SO(6)/SO(5) coset structure (which describe five light degrees of freedom: four belonging to the Higgs and one belonging to a new light CP-odd scalar singlet) the existence of an extra gauge singlet in the Higgs sector influence the strength of the phase transition and its CP-odd couplings provide the extra source of CP violation. Furthermore, at low energy, this set up consisting of the Higgs plus a CP-odd singlet coupled to the fermions, provides the most minimal scenario capable of explaining the baryon asymmetry.

Speaker: Francesco Riva (IFAE)

Slides Francesco_Riva_PONT2011.pdf

23 Helical magnetic fields from inflation and their evolution.

I discuss the generation of helical magnetic fields in single field inflation induced by an axial coupling of the electromagnetic field to the inflaton. In slow roll, such a coupling always leads to a blue spectrum, P_B ~ k, while a short deviation does not result in strong modifications to the shape of the spectrum. Then I consider the subsequent evolution of the spectrum during the inverse cascade and viscous damping of the helical magnetic fields. Although power is moved from small to larger scales, the magnetic fields in this scenario are too weak to provide the seeds for the observed fields in galaxies and clusters; except for low scale inflation with very strong axial coupling, a case where the perturbative treatment of the theory may break down. If time permits, I discuss possible ways of amplification of primordial seed magnetic fields at late times through an axial coupling of electromagnetism to a dark energy scalar field.

Speaker: Dr Lukas Hollenstein (Département de Physique Théorique, Université de Genève)

Slides hmf_avignon.pdf

24 New mechanism of generation of cosmological magnetic fields below electroweak scale

I will present a new mechanism of generation of cosmological magnetic fields below electroweak scale and discuss their subsequent evolution. The mechanism is a byproduct of oscillations of sterile neutrinos, also responsible for baryo and leptogenesis and dark matter production.

Speaker: Dr Oleg Ruchayskiy (CERN)

Slides avignon-2011-04.pdf

25 Dark energy with non-adiabatic sound speed

I will describe the prospects of detecting dark energy perturbations from Planck and a LSST-like survey. I will also discuss the initial conditions for dark energy perturbations in the radiation and matter epochs, generalizing the usual adiabatic ones to include the sound speed effect.

Speaker: Dr Guillermo Ballesteros (University of Padova)

Slides 5.Ballesteros.pdf

26 Dark energy and inhomogeneity

I discuss how the averaging problem confuses our potential understanding of dark energy by considering the backreaction from density perturbations to second-order in the concordance model: this effect leads to at least a 10% increase in the dynamical value of the deceleration parameter, and could be significantly higher. Large Hubble-scale inhomogeneity has not been investigated in much detail, and could conceivably be the cause of apparent cosmic acceleration. I discuss void models which defy the Copernican principle in our Hubble patch, and describe how we can potentially rule out these models.

Speaker: Chris Clarkson (University of Cape Town)

Slides 6.Clarkson.pdf

16:30 Coffee Break

Contributed Talks

27 A large void versus the cosmological constant: still no verdict.

The evidence for the cosmological constant Lambda relies crucially on the postulate that we do not live in a special place: the cosmological principle. To strengthen the evidence, we must test that postulate and rule out alternatives. In this talk I will show how a very large spherically symmetric void can fit all existing evidence for Lambda simultaneously: the CMB, BAO, SN and H0, while using only Dark Matter and General Relativity but no Lambda. The purpose is to point out the different roles of assumptions and observations in the evidence for Lambda. Finally I will discuss the tests that should be performed in the future to rule out such a scenario, putting Lambda on a firmer basis.

Speaker: Dr Wessel Valkenburg (ITTK, RWTH Aachen)

Slides 7.valkenburg.pdf

28 Backreaction in the relativistic Zel’dovich approximation

Zel’dovich’s approximation is in Newtownian cosmology a practical tool to investigate the evolution of mildly nonlinear regions of the Universe. Its extension to the relativistic case is important for the investigation of the backreaction of inhomogeneities on the evolution history of spatial domains of the Universe. This talk presents a Lagrangian framework that allows for a one to one correspondence of Newtownian and general relativistic quantities and provides a non-perturbative backreaction model, together with domain-dependent quantitiative estimates of the backreaction effect.

Speaker: Alexander Wiegand (Universitaet Bielefeld)

Slides pont2011wiegand.pdf

29 Growing neutrino dark energy

The "growing neutrino scenario" solves the coincidence problem of dark energy by a growing cosmological value of the neutrino mass which emerges from an interaction between a scalar field and the neutrino. The field mediated attraction between neutrinos induces the formation of large scale neutrino lumps in a recent cosmological epoch. I will show that the non-linearities in the scalar field equation of motion stop the further increase of the neutrino mass when sufficiently dense and large lumps are formed. Consequently, the neutrino induced gravitational potential is substantially reduced when compared to linear estimates. I will also demonstrate that inside a lump, the possible time variation of fundamental constants is much smaller than their cosmological evolution. This feature may reconcile current geophysical bounds with claimed cosmological variations of the fine structure constant.

Speaker: Nelson Nunes (U. Heidelberg)

Slides neu15.pdf

30 Anisotropic stress and (background) stability of modified gravity models

The existence of an effective anisotropic stress at late times, which in this case has a purely geometrical origin, seems to be a characteristic of higher order gravity models, and its detection will be a smoking gun for departures from General Relativity (GR), for example in future weak lensing surveys. However, no departure from GR has been as yet observed. In my talk, I will discuss and investigate the possibility of constructing a class of modified gravity models of the general f(R,G) type, able to "hide" from weak lensing experiments by giving a GR-like behavior for the lensing potentials, i.e having a zero anisotropic stress. For both a de Sitter and matter background I will identify models with the desired property, and will discuss the difficulties arising from such constructions, such as instabilities and extreme fine tuning. In particular, as I will show, models with zero anisotropic stress in a de Sitter spacetime, suffer from a background singularity, that makes it impossible to reach de Sitter evolution. Motivated by the latter fact, I will proceed to discuss the link between the effective anisotropic stress and the (background) stability of the model as well as the presence of extra degrees of freedom, which seems to be a general feature of higher order gravity models.

Speaker: Mr Ippocratis Saltas (University of Sussex)

Slides presentation_Avignon.pdf

31 The Coincidence Problem in a Phantom Cyclic Model of the Universe

In a phantom dark energy model, the energy density increases with the expansion of the Universe, allowing it to go through standard cycles of radiation/matter domination, followed by a dark energy/inflationary phase. There is a period in each cycle where the dark energy and matter densities are comparable. Since the cycles repeat infinitely, the Universe spends a substantial portion of its lifetime in such a state; this significantly ameliorates the coincidence problem.

Speaker: Ms Hui-Yiing Chang (Vanderbilt University)

Slides physics_conference,_PONT,_France,_2011,_presentn.pdf physics_conference,_PONT,_France,_2011,_presentn.pptx

32 The Strained State Cosmology

Space-time as a four-dimentional continuum has an evident similarity with ordinary three-dimensional continua, apart from the Lorentzian signature of the metric tensor. Since it has physical properties related to its interaction with matter, the analogy suggests that it can behave as elastic continua do, provided that general covariance is preserved. The theory that will be presented describes how to implement these ideas into a formally consistent cosmological scenario. The theory successfully accounts for the accelerated expansion and turns out to be consistent with a number of typical cosmological tests such as light elements abundances, acoustic horizon of the CMB, large scale structure formation and SnIa luminosity/redshift dependence.

Speaker: Prof. Angelo Tartaglia (Politecnico di Torino)

Slides PONT11AT.pdf Strained State Cosmology

Wednesday 20 April

Observational Cosmology

33 CMB with Planck

Speaker: Fabio Finelli (INAF)

Slides 1.Finelli.pdf

34 Tests of acceleration

Speaker: Martin Kunz (Departement de Physique Theorique-Universite de Geneve)

Slides acceleration_avignon_mk.pdf acceleration_avignon_mk.ppt

10:30 Coffee Break

35 Matter surveys

Speaker: Will Percival (University of Portmsouth)

Slides Percival-Avignon-20-04-11.pdf Percival-Avignon-20-04-11.pptx

36 Non gaussianities

Speaker: Emiliano Sefusatti (CEA/Saclay)

Slides 4.Sefusatti.pdf

12:30 Lunch Break

Contributed Talks

37 Cosmological Implications of Massive Clusters in the Early Universe

We describe recent observations of massive, high redshift clusters of galaxies, and show that they appear to be in tension with best fit WMAP 7 LCDM cosmological parameters. We show that we can alleviate the tension by introducing the non Gaussianity parameter fnl. We discuss other recent work on these massive objects.

Speaker: Dr ben hoyle (University of Barcelona)

38 N-body simulations with generic non-Gaussian initial conditions

The statistical nature of the initial conditions of the universe can be most directly probed by observations of the early universe, e.g. by the cosmic microwave background. However, primordial non-Gaussianity can also leave measurable signatures in the large-scale structure of the late-time universe. Observables like the galaxy cluster mass function, the galaxy bias and bispectrum are affected by the departures from Gaussianity in distinctive ways. In order to derive constraints on primordial non-Gaussianity from upcoming data of large-scale structure surveys, accurate theoretical modeling is needed. To this end, N-body simulations are indispensable, since the non-linear gravitational evolution has to be taken into account. Here, we introduce a prescription for setting up non-Gaussian initial conditions for N-body simulations, where the departures from Gaussianity are specified by a given primordial bispectrum. Using this technique, we are able to run N-body simulations for the local and non-local types of non-Gaussianity. Results of these simulations regarding the halo mass function and the halo bias are presented and implications for large-scale structure probes of non-Gaussianity are discussed. More details can be found in arXiv:1006.5793 and arXiv:1102.3229.

Speaker: Dr Christian Wagner (ICC, University of Barcelona)

Slides avignon.pdf avignon.ppt

39 Non-Gaussianities in halo clustering properties

Using excursion set theory, and its path-integral formulation, it is possible to analytically compute several properties of the dark matter halos, like their distribution in mass, formation history, and merging rate. The inclusion of non-Gaussian initial conditions establishes an interesting connection between primordial conditions and observable features of the large-scale universe. In this talk, I will briefly introduce the computational techniques and then describe the results for halo mass functions and conditional probabilities with non-Gaussian initial conditions.

Speaker: Dr Andrea De Simone (Institut de Physique Theorique-Ecole Polytechnique Federale de L)

Slides DeSimone_PONT.pdf

40 Angular Clustering in Photometric Surveys: a new window for redshift distortions.

Near future cosmology will see the advent of wide area photometric galaxy surveys, such as the DES, PanSTARRS and LSST that extent to high redshifts (z ~ 2) but with poor radial distance resolution. In such cases splitting the data into redshift bins and looking at angular clustering will become the standard approach to extract cosmological information or to study the nature of dark energy through the Baryon Acoustic Oscillations (BAO) probe. In this talk I will present a comprehensive model for this clustering signal at large angular scales as a function of redshift and bin width, including all relevant effects, namely nonlinear gravitational clustering, bias, redshift space distortions and photo-z uncertainties. We also discuss, and test against simulations, a model for the full covariance matrix characterizing the angular correlation measurements. One interesting outcome is the potential of photometric surveys to yield constrains in the growth of structure through redshift space distortions. Hence we discuss the prospects for a full shape analysis of the angular correlation function at BAO scales in forthcoming photometric surveys.

Speaker: Dr Martin Crocce (ICE)

Slides 4.Crocce.pdf

41 What galaxy surveys really measure

Galaxy redshift surveys measure the number of galaxies per solid angle as a function of redshift. This observation is then used to infer the underlying matter power spectrum and learn about structure formation and cosmological parameters. The link between observation and matter density is however not as simple as it is usually assumed. It is know since a long time that galaxy number density measurements are affected by redshift-space distortion. In this talk I will show that in addition to this well-known correction, various relativistic effects enter in the relation between the observed galaxy number density and the underlying physical quantities, i.e. density perturbation, peculiar velocity and gravitational potential. I will show how to express the observable in terms of gauge invariant variables and I will discuss the various corrections to the standard result. At small redshift, the dominant contribution comes from peculiar velocities of galaxies, whereas at large redshift magnification gives the largest contribution. These corrections are relevant at large scales and are large enough to be observed in future galaxy redshift surveys.

Speaker: Dr Camille Bonvin (University of Cambridge)

Slides bonvin_PONT.pdf

16:10 Coffee Break

Contributed Talks

42 Framework for performance forecasting and optimization of CMB B-mode observations in presence of astrophysical foregrounds

We derived a semi-analytic formalism for performance forecasting and optimization for future CMB experiments. The formalism accounts for statistical uncertainties due to the CMB sky statistics as well as presence of the foreground signals. We model the effects of subtraction of these using parametric maximum likelihood technique. As an illustration of this formalism, we performed in this work both performance forecasting and optimization of future satellite CMB B-mode observations.

Speaker: Mr Josquin Errard (Laboratoire Astroparticule et Cosmologie)

Slides presentation_PONT_2011.key

43 From k-essence to generalised Galileons and beyond...

We construct the most general scalar field theory whose action depends on derivatives of order two or less and is polynomial in the second derivatives of the field, under the condition that the equations of motion stay second order on flat space-time. This generalises k-essence, Galileons, k-Mouflage, the kinetically braided scalars, as well as the Euler hierarchies of Fairlie et al., avoiding at the same time ghost-like degrees of freedom. The covariantization of such models, as well as future directions, are also discussed.

Speaker: Mr George Zahariade (Laboratoire APC)

Slides PONT2011_Zahariade_Var.pptx

44 Modeling the shapes of dark matter halos

We combine the physics of the ellipsoidal collapse model with the excursion set theory to study the shapes of dark matter halos. In particular, we develop an analytic approximation to the nonlinear evolution that is more accurate than the Zeldovich approximation, and we provide simple physical explanations for some empirical fitting formulae obtained from numerical studies. Comparison with simulations is challenging, as there is no agreement about how to define a non-spherical gravitationally bound object. Nevertheless, we find that our model matches the conditional minor-to-intermediate axis ratio distribution rather well, although it disagrees with the numerical results in reproducing the minor-to-major axis ratio distribution. We suggest that some of the disagreement with some previous numerical studies may be alleviated if we consider only isolated halos.

Speaker: Graziano Rossi (Korea Institute for Advanced Study (KIAS))

Slides 8.Rossi.pdf

45 Cosmological Perturbations in Horava-Lifshitz Gravity

We consider the most general action of Horava-Lifshitz Gravity in the presence of scalar matter with and without the projectability condition, determine the actual number of propagating degrees of freedom of the linearized theory on the cosmological background and discuss the stability of the extra scalar mode that the theory exhibits.

Speaker: Dr Alessandro Cerioni (University of Bologna)

Slides PONT_2011-_Cerioni.pdf

19:30 Banquet

Thursday 21 April

Dark Matter

46 Indirect Detection of Dark Matter: Status and Prospects

Speaker: Lars Bergstrom (Stockholm University)

Slides Bergstrom.pdf

47 Dark Matter direct detection

Speaker: Eric Armengaud (CEA Saclay)

Slides 2.Armengaud.pdf

10:30 Coffee Break

48 News from the front of DM theories

Speaker: Tracy Slatyer (Harvard University)

Slides 3.Slatyer.pdf

49 DM/Baryo connection

Speaker: John March-Russell (Oxford)

Slides 4.MarchRussell.pdf

12:30 Lunch Break

Contributed Talks

50 Spontaneous Genesis

N.A.

Speaker: Mr Matthew McCullough (Oxford University)

Slides McCullough.pdf

51 Non-Abelian Discrete Dark Matter

We consider the minimal model in which dark matter is stabilized by a non-Abelian discrete symmetry. The symmetry group is taken to be D_3, which is the smallest non-Abelian finite group. The minimal model contains (nontrivial) singlet and doublet scalar representations of D_3 which couple to the Standard Model fields via the Higgs portal. This construction predicts two species of dark matter over much of the parameter space. Nontrival interactions under D_3 lead to a novel thermal history of dark matter, while the multi-component nature of dark matter can be tested by future direct detection experiments.

Speaker: Josef Pradler (Perimeter Institute for Theoretical Physics)

Slides PONT2011.pdf

52 Dark matter direct detection: a closer look at the astrophysical uncertainties

Although there are great expectations from the LHC to shed light on physics beyond the Standard Model and an eventual embedding of a dark matter candidate within it, a clean handle on the dark matter puzzle will come only from direct or indirect detection signals of dark matter particles within dark matter halos. There are classes of dark matter candidates for which it is indeed feasible to extract such signals, for instance measuring the interaction of a dark matter particle from the local population within a laboratory detector. A direct detection signal scales linearly with the local number density of dark matter particles and depends also on their local velocity distribution. In this talk I will show how Bayesian methods recently reduced considerably the uncertainties on those quantities. For instance, given a Galactic mass model and assuming a spherically symmetric dark matter halo, the local dark matter density can be now determined with an accuracy of approximately the 10%. I will also discuss how such an approach, combined with Eddington's inversion formula for the phase-space density, can be used to determine the dark matter local velocity distribution.

Speaker: Dr Riccardo Catena (ITP, Heidelberg)

Slides 3.Catena.pdf

53 Dark matter searches with the Fermi-LAT

Because of its good sensitivity and angular resolution, as well as energy coverage which includes 1-300 GeV range, the Fermi-LAT is considered to be a prime tool for an indirect search of a signal of a WIMP annihilation. I will review current dark matter search strategies by the Fermi-LAT team, with a particular emphasis on the searches for cosmological DM annihilation in the extragalactic diffuse emission.

Speaker: Gabrijela Zaharijas (CEA Saclay)

Slides 4.Zaharijas.pdf

54 Constraining the dark matter density profile of milky way with gamma-rays with Fermi-LAT

We study the abilities of the Fermi-LAT instrument on board of the Fermi mission to constrain the dark matter density profile and the effect the uncertainties in the dark matter distribution could have to constrain dark matter properties, as annihilation cross section, mass and branching ratio into dominant annihilation channels.

Speaker: Dr Nicolas Bernal (Uni Bonn)

Slides pont.pdf

55 Indirect Search for Dark Matter with the ANTARES Neutrino Telescope

The ANTARES Collaboration is now operating the largest water Cherenkov neutrino telescope in the Nothern hemisphere. The apparatus, completed in May 2008, comprises 12 detection lines and a multidisciplinary instrumentation line installed at a depth of about 2500 m in the Mediterranean Sea offshore from France. The goals of ANTARES are among others the search for astrophysical neutrino point sources and for neutrinos produced in self-annihilation of Dark Matter particles. In that respect, the most promising sources of neutrino emission are the Sun and the Galactic Centre, where Dark Matter particles from the galactic halo are expected to accumulate, which should produce a clean signal much less affected by astrophysical undertainties and/or backgrounds than for indirect detection with gamma rays. Prior to its completion, ANTARES has been taking data for more than a year in an intermediate setup with a five and a ten line detector configuration. First results on the search for Dark Matter annihilations in the Sun with the data recorded in 2007 and 2008 are presented, as well as sensitivity studies on Dark Matter searches with the full ANTARES detector and the future large undersea cubic-kilometer neutrino telescope studied by the KM3NeT consortium. A comparison with respect to predictions on neutrino fluxes from Dark Matter annihilations in the framework of CMSSM and UED models will be presented.

Speaker: Vincent Bertin (Faculte des Sciences de Luminy)

Slides 6.Bertin.pdf 6.Bertin.ppt

16:30 Coffee Break

Contributed Talks

56 Dark matter relic density at one loop level - effective coupling approach

The lightest neutralino as a cold dark matter candidate has been widely studied. Generally, tree-level calculations of its (co-)annihilation cross sections are used to predict the relic density, which leads to constraints on the parameter space. It has been known that these cross sections can change by order 10% at one loop level. However, calculating these one loop corrections is computationally demanding and time consuming due to large number of diagrams. On the other hand, with the launch of the Planck satellite the relic density of dark matter will be experimentally determined at a percent accuracy. Matching this accuracy requires the inclusion of at least leading radiative corrections. We use the approach of effective couplings in order to reduce the computational stress. In this work, we estimate the resulting corrections to the predicted neutralino relic density, and investigate the available parameter space at one loop level.

Speaker: Ms Suchita Kulkarni (BCTP and Physics Institute, Bonn)

Slides 7.Kulkarni.pdf

57 Dark Matter Effective Theory

A large number of models for Dark Matter have been put forward in recent years and compared with experimental data. A true model-independent analysis of the possible interaction terms is still not on the horizon. I will present the first step towards a future comprehensive analysis which starts with constructing a well defined effective theory for Dark Matter. We can now use our results for direct and indirect searches as well as for the study of Dark Matter genesis. Our approach allows for systematic improvements via quantum corrections, at the effective Langrangian level. While classifying our terms we made the discovery of the existence of interesting flavor-violating operators in the dark sector awaiting to be tested experimentally.

Speaker: Eugenio Del Nobile (Centre for Particle Physics Phenomenology CP3-Origins)

Slides Eugenio_Del_Nobile-Dark_Matter_Effective_Theory.key Eugenio_Del_Nobile-Dark_Matter_Effective_Theory.pdf

58 Electroweak lights from Dark Matter annihilation

The computation of the energy spectra of Standard Model particles originated from the annihilation/decay of dark matter is a foudamental ingredient to investigate the possibility of its indirect detection. We compute how the inclusion of electroweak corrections signicantly alter such spectra when the mass of dark matter particles is larger than the electroweak scale. A wide overview of these effects will be discussed.

Speaker: Dr Alfredo Urbano (IFAE, Universitat Autonoma di Barcelona & Università del Salento)

Slides 9.Urbano.pdf

59 Gamma-Ray Lines from Radiative Dark Matter Decay

The decay of dark matter particles which are coupled predominantly to charged leptons has been proposed as a possible origin of excess high-energy positrons and electrons observed by cosmic-ray telescopes PAMELA and Fermi LAT. Even though the dark matter itself is electrically neutral, the tree-level decay of dark matter into charged lepton pairs will generically induce radiative two-body decays of dark matter at the quantum level. Using an effective theory of leptophilic dark matter decay, we calculate the rates of radiative two-body decays for scalar and fermionic dark matter particles. Due to the absence of astrophysical sources of monochromatic gamma rays, the observation of a line in the diffuse gamma-ray spectrum would constitute a strong indication of a particle physics origin of these photons. We estimate the intensity of the gamma-ray line that may be present in the energy range of a few TeV if the dark matter decay interpretation of the leptonic cosmic-ray anomalies is correct and comment on observational prospects of present and future Imaging Cherenkov Telescopes, in particular the CTA.

Speaker: David Tran (Technical University of Munich)

Slides tran_pont.pdf

60 Light Dark Matter and Neutrino Telescopes

I discuss the possibility of light dark matter as an explanation for the anomalies seen at the direct detection experiments DAMA, CoGeNT and CRESST. I derive new strong limits on light dark matter from neutrino telescopes. Finally, I introduce a realization of light dark matter in a singlet extension of the MSSM.

Speaker: Mr Martin Winkler (Technische Universität München)

Slides PontWinkler.pdf

61 Relic gravitational waves from light primordial black holes

The energy density of relic gravitational waves (GWs) emitted by primordial black holes (PBHs) is calculated. We estimate the intensity of GWs produced at quantum and classical scattering between PBHs, the classical graviton emission from the PBH binaries in the early Universe, and the graviton emission due to PBH evaporation. If nonrelativistic PBHs dominated in the cosmological energy density prior to their evaporation, the probability of formation of dense clusters of PBHs and their binaries in such clusters would be significant and the energy density of the generated gravitational waves in the present day universe could exceed that produced by other known mechanisms. The intensity of these gravitational waves would be maximal in the GHz frequency band of the spectrum or higher and this makes their observation very difficult by the existing detectors. However, the low frequency part of the spectrum in the range $f\sim 10^{-4}-10^2$ Hz may be detectable by the planned space interferometers DECIGO/BBO. For a sufficiently long duration of the PBH matter dominated stage the cosmological energy fraction of GWs from inflation would be noticeably diluted.

Speaker: Damian Ejlli (University Of Ferrara)

Slides 12.Ejlli.pdf

Friday 22 April

The Accelerating Universe

62 The anthropic universe

Speaker: Yasunori Nomura (UC Berkeley)

Slides 1.Nomura.pdf

63 Galileon

Speaker: Claudia de Rham (Université de Genève)

Slides PONT_Avignon_April2011_1.pptx

10:30 Coffee Break

64 Quantum gravity

Speaker: Oriol Pujolas Boix

Slides 3.Pujolas.pdf 3.Pujolas.ppt

65 White smokes and Dark smokes in cosmology

Speaker: Sean Carroll (Caltech)

Slides smokes.pdf smokes.ppt