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...
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 โtribridโ structure in the superpotential and on a โHeisenberg symmetryโ for solving the ฮท-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...
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...
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...
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...
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...
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...
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....
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...
Dr
Lukas Hollenstein
(Dรฉpartement de Physique Thรฉorique, Universitรฉ de Genรจve)
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...
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.
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.
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...
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...
Alexander Wiegand
(Universitaet Bielefeld)
19/04/2011, 17:15
Zelโdovichโs 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...
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...
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...
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...
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...
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.
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...
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...
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...
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...
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...
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...
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.
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...
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...
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...
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.
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...
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...
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...
Dr
Alfredo Urbano
(IFAE, Universitat Autonoma di Barcelona & Universitร 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...
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...
Mr
Martin Winkler
(Technische Universitรคt Mรผnchen)
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.
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...
