Horaire:Tuesday, 30. July 2013 - 14:00
We show that density perturbations seeded by the inflaton can be suppressed when having additional light degrees of freedom contributing to the production of perturbations. The inflaton fluctuations affect the light field dynamics by modulating the length of the inflationary period, hence produce additional density perturbations in the post-inflationary era. Such perturbations can cancel those generated during inflation as both originate from the same inflaton fluctuations.
Orateur:Dhiraj Kumar Hazra
Home Institute:APCTP, Korea
Horaire:Thursday, 18. July 2013 - 14:00
Power spectrum from the primordial perturbations can be reconstructed directly from the Cosmic Microwave Background (CMB) observations in a model independent way. In this context, error sensitive Richardson-Lucy (RL) deconvolution algorithm has been used previously to reconstruct the power spectrum from CMB data. In this talk I shall initially discuss earlier literatures towards this reconstruction. After providing a broad overview of the method I shall discuss the scopes of improvizing the algorithm to make it faster and efficient and to broaden its applications.
Horaire:Monday, 15. July 2013 - 14:00
Large scale distribution of galaxies is believed to be determined by the dark matter distribution, but their
detailed relationship remains unknown. Weak lensing and galaxy clustering can be used to study their
Home Institute:Montana State University
Horaire:Tuesday, 2. July 2013 - 14:00
Einstein's theory has passed all tests to date in the quasi-stationary weak-field, where gravitational dynamics are weak and quadrupolar, while velocities are small relative to the speed of light. The highly non-linear and dynamical regime of the gravitational interaction, however, remains mostly unexplored. The future detection of gravitational waves will open a window into this regime that will allow us to confront Einstein's predictions to unprecedented levels.
Orateur:Sergei V. Ketov
Home Institute:KIPMU, Tokyo Metropolitan University
Horaire:Wednesday, 26. June 2013 - 14:00
Early universe cosmology can be described in the theoretical framework of modified gravity and quintessence. Our recent results devoted to the Starobinsky inflation, pre-heating and re-heating, and their relation to the observational cosmology, are reviewed in the context of f(R) gravity and are extended to the F(R) supergravity.
Orateur:Séminaire joint Neutrinos/Théorie
Home Institute:MPI, Munich
Horaire:Tuesday, 25. June 2013 - 14:00
In the laboratory search for Dark Matter via direct detection, a great difficulty is that the signal is rather unspecific, simply a small nuclear recoil. Therefore it is difficult, in such low rate experiments, to say if some unexplained events are a true signal or perhaps some unsuspected background.
Horaire:Monday, 24. June 2013 - 14:00
If the formation and evaporation of a black hole is a unitary process, then an observer falling into a sufficiently old black hole will experience a violent shock, or "firewall", at the horizon. This conclusion is dramatic, as it appears to contradict the equivalence principle. I will discuss proposals for how to avoid firewalls and why they fall short. I will speculate that the equivalence principle may nevertheless be upheld, at the expense of the ubiquity of the vacuum state.
Home Institute:Radboud University Nijmegen
Horaire:Thursday, 27. June 2013 - 14:00
In recent years the major developments in Loop Quantum Gravity have arisen in the covariant framework (spinfoam) where the dynamics is coded by transition amplitudes. These provide an evolution for "quanta of spacetime" in terms of a local product of interaction vertices, reconstructing a Lorentzian spacetime. The first part of the talk will be devoted to a general presentation of these results.
Orateur:Mikael Von Strauss
Home Institute:Stockholm University
Horaire:Tuesday, 11. June 2013 - 14:00
Finding consistent generalisations of General Relativity has been very challenging, but its pursuit has (at least) two strong motivations. One is to find out if it is possible to confront cosmological observations without introducing Dark sectors. The other is that it is very rare in field theory to come across new consistent theories and history has taught us that, once they are found, they often have a place in our understanding of nature.
Lieu:454A Luc Valentin
Horaire:Monday, 3. June 2013 - 14:00
We focus on zero-temperature phases of strongly-coupled holographic superfluids at finite density. We show that they can be classified according to their scaling symmetries, as well as the behavior of the electric flux in the deep IR. In the presence of a running scalar, these phases may display hyperscaling violation, which measures the breaking of rigid scaling symmetry in the IR.