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

Session

Contributed Talks

18 Apr 2011, 14:30

Chambre du Trésorier (Palais des Papes, Avignon)

53. Nonstandard tensor modes from a pseudoscalar inflaton

Lorenzo Sorbo (University of Massachusetts, Amherst)

18/04/2011, 14:30

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...

66. Gauge Non-Singlet Matter Inflation in Supergravity

Dr Stefan Antusch (MPI of Physics, Munich)

18/04/2011, 14:50

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...

32. Cosmological perturbations in the UV-protected inflation

Dr Yuki Watanabe (LMU Munich)

18/04/2011, 15:10

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...

62. Can thermal masses constrain the reheating temperature?

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

18/04/2011, 15:30

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...

35. Imperfect Dark Energy of Kinetic Gravity Braiding

Alexander Vikman (CERN)

18/04/2011, 15:50

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...

46. Minimal models of inflation -- connecting cosmology and experiment

Dr Fedor Bezrukov (LMU)

18/04/2011, 16:10

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...

69. Unitarizing Higgs inflation

Dr Hyun Min Lee (CERN)

18/04/2011, 17:00

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...

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

Dr Guido D'Amico (NYU)

18/04/2011, 17:15

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...

60. Primordial fluctuations and non-Gaussianities in a Galilean theory

Dr Sebastien Renaux-Petel (University of Cambridge)

18/04/2011, 17:30

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...

54. Inflection point inflation with MSSM Higgs fields

Mr Arindam Chatterjee (University of Bonn)

18/04/2011, 17:45

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...

45. Supercurvaton

Vittoria Demozzi (LMU Munich)

18/04/2011, 18:00

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...

33. Vector fields and Loop Quantum Cosmology

Mr Michal Artymowski (IFT, University of Warsaw)

18/04/2011, 18:15

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....

34. Supersonic Electroweak Baryogenesis: Achieving Baryogenesis from Fast Bubble Walls

Dr Jose Miguel No (IPhT CEA Saclay)

19/04/2011, 14:30

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...

61. Electroweak Baryogenesis from a Composite Higgs Sector

Francesco Riva (IFAE)

19/04/2011, 14:50

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...

38. Helical magnetic fields from inflation and their evolution.

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

19/04/2011, 15:10

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...

68. New mechanism of generation of cosmological magnetic fields below electroweak scale

Dr Oleg Ruchayskiy (CERN)

19/04/2011, 15:30

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.

41. Dark energy with non-adiabatic sound speed

Dr Guillermo Ballesteros (University of Padova)

19/04/2011, 15:50

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.

4. Dark energy and inhomogeneity

Chris Clarkson (University of Cape Town)

19/04/2011, 16:10

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...

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

Dr Wessel Valkenburg (ITTK, RWTH Aachen)

19/04/2011, 17:00

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...

73. Backreaction in the relativistic Zel’dovich approximation

Alexander Wiegand (Universitaet Bielefeld)

19/04/2011, 17:15

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...

67. Growing neutrino dark energy

Nelson Nunes (U. Heidelberg)

19/04/2011, 17:30

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...

40. Anisotropic stress and (background) stability of modified gravity models

Mr Ippocratis Saltas (University of Sussex)

19/04/2011, 17:45

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...

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

Ms Hui-Yiing Chang (Vanderbilt University)

19/04/2011, 18:00

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...

30. The Strained State Cosmology

Prof. Angelo Tartaglia (Politecnico di Torino)

19/04/2011, 18:15

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...

36. Cosmological Implications of Massive Clusters in the Early Universe

Dr ben hoyle (University of Barcelona)

20/04/2011, 14:30

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.

63. N-body simulations with generic non-Gaussian initial conditions

Dr Christian Wagner (ICC, University of Barcelona)

20/04/2011, 14:50

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...

55. Non-Gaussianities in halo clustering properties

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

20/04/2011, 15:10

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...

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

Dr Martin Crocce (ICE)

20/04/2011, 15:30

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...

50. What galaxy surveys really measure

Dr Camille Bonvin (University of Cambridge)

20/04/2011, 15:50

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...

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

Mr Josquin Errard (Laboratoire Astroparticule et Cosmologie)

20/04/2011, 16:40

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...

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

Mr George Zahariade (Laboratoire APC)

20/04/2011, 16:55

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...

74. Modeling the shapes of dark matter halos

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

20/04/2011, 17:10

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...

75. Cosmological Perturbations in Horava-Lifshitz Gravity

Dr Alessandro Cerioni (University of Bologna)

20/04/2011, 17:25

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.

64. Spontaneous Genesis

Mr Matthew McCullough (Oxford University)

21/04/2011, 14:30

N.A.

70. Non-Abelian Discrete Dark Matter

Josef Pradler (Perimeter Institute for Theoretical Physics)

21/04/2011, 14:50

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...

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

Dr Riccardo Catena (ITP, Heidelberg)

21/04/2011, 15:10

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...

56. Dark matter searches with the Fermi-LAT

Gabrijela Zaharijas (CEA Saclay)

21/04/2011, 15:30

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...

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

Dr Nicolas Bernal (Uni Bonn)

21/04/2011, 15:50

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.

72. Indirect Search for Dark Matter with the ANTARES Neutrino Telescope

Vincent Bertin (Faculte des Sciences de Luminy)

21/04/2011, 16:10

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...

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

Ms Suchita Kulkarni (BCTP and Physics Institute, Bonn)

21/04/2011, 17:00

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...

52. Dark Matter Effective Theory

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

21/04/2011, 17:15

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...

49. Electroweak lights from Dark Matter annihilation

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

21/04/2011, 17:30

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...

58. Gamma-Ray Lines from Radiative Dark Matter Decay

David Tran (Technical University of Munich)

21/04/2011, 17:45

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...

65. Light Dark Matter and Neutrino Telescopes

Mr Martin Winkler (Technische Universität München)

21/04/2011, 18:00

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.

71. Relic gravitational waves from light primordial black holes

Damian Ejlli (University Of Ferrara)

21/04/2011, 18:15

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...