Schedule 2007-2008
Friday October
5 (University of Amsterdam)
1400h: Seminar in room REC I.201
Speaker: Daniel Wesley (DAMPT, Cambridge)
Title: Primordial Magnetic Fields and Cosmic Strings
Abstract:
Galaxies and clusters are suffused with magnetic fields of roughly micro-Gauss strength, but the origin of these fields remains both mysterious and controversial. There is evidence that these fields arose from weak primordial fields, created after inflation, that were subsequently amplified. A cosmic string network provides an excellent candidate for producing these fields. I will describe recent calculations of the expected fields produced by the string network and prospects for future constraints on this model.
1530h: Journal club discussion in ITP lounge
Speaker: Daan Meerburg (ITP/API, UVA)
Daan will discuss the recent paper
"Multifield DBI Inflation and Non-Gaussianities"
by H. Huang, G. Shiu and B. Underwood
Friday November
9 (University of Leiden)
1400h: Seminar
Speaker: Ruth Gregory (Durham University)
Title: Spinflation
Abstract:
Recent ideas from string theory view our universe as a brane, moving in compact extra dimensions. I will review this scenario and discuss how angular momentum on the internal manifold might lead to new phenomena in the evolution of the universe.
1530h: Journal club discussion
Speaker: Koenraad Schalm (ILTP)
Koenraad will discuss the recent paper
"Axion Inflation and Gravity Waves in String Theory"
by R. Kallosh, N. Sivanandam and M. Soroush [hep-th:0710.3429]
Friday December
7 (University of Utrecht)
1400h: Seminar
Speaker: Patrick Peter (Institut d'Astrophysique de Paris)
Title: Can non-inflationary cosmology be made consistent with observations?
Abstract:
The inflationary paradigm has made many predictions that have been well tested or will soon be tested with impressive precision. Is it however the definite model of the early Universe? There exists a general class of plausible challengers, stemming mostly from high energy theories (string or quantum gravity), which do not include a phase of inflation but nonetheless has reasonnable observable consequences. In particular, a simple quantum cosmology case can be argued to produce a scale invariant spectrum, in agreement with current observations. Such a model also yields to a consistency relation that is sufficiently different from that obtained in the slow-roll approximation to be testable in the near future.
1530h: Journal club discussion
Speaker: Tomas Janssen (ITP Utrecht)
Tomas will discuss the recent paper
"Local Void vs Dark Energy: Confrontation with WMAP and Type Ia Supernovae" by Stephon Alexander, Tirthabir Biswas, Alessio Notari and Deepak Vaid [astro-ph:0712.0370]
Friday February
1 (University of Utrecht)
1400h: Seminar
Speaker: Laura Covi (DESY)
Title: How to see Gravitino DM
Abstract:
We review the case for gravitino Dark Matter and discuss in particular BBN constraints on the nature of the NLSP. We describe in detail a couple of scenarios that allow to relax such bounds and their signatures both in colliders and astrophysical observations.
1530h: Journal club discussion
Speaker: Jurjen Koksma (ITP Utrecht)
Jurjen will discuss the recent paper
"Detection of primordial non-Gaussianity (f_{NL}) in the WMAP 3-year data at above 99.5% confidence" by A. Yadav and B. Wandelt [astro-ph:0712.1148]
Friday March 7
(University of Amsterdam)
1400h: Seminar
Speaker: Wessel Valkenburg (LAPTH, Annecy)
Title: On constraining inflationary parameter space
Abstract:
The paradigm of inflation offers an explanation for the observed cosmic perturbations. I will discuss the class of minimally coupled (effective) single scalar fields as the inflaton, and focus on a comparison of different approximations commonly used to constrain (inflationary) cosmological parameters with the observations. Choosing different priors on cosmological parameters will turn out to have a significant effect on the result of any analysis. For example, an estimation of the scale of inflation changes significantly under different parameterizations (for the same physics), hence leads to different expectations for future observations of primordial gravitational waves. Eventually, I will present the latest constraints on the evolution of the Hubble factor during inflation, thereby constraining the inflaton potential.
1530h: Journal club discussion
Speaker: TBA
Friday April 4
(University of Leiden)
1400h: Seminar
Speaker: Ben Craps (VUB)
Title: Quantum Resolution of Cosmological Singularities using AdS/CFT
Abstract:
The AdS/CFT correspondence is used to describe five-dimensional cosmology with a big crunch singularity in terms of N=4 supersymmetric SU(N) gauge theory on R times S3 deformed by an unstable potential. The big crunch singularity in the bulk corresponds in the boundary theory to a scalar field rolling to infinity in finite time. We generalize the method of self-adjoint extensions to define consistent unitary quantum evolution in the boundary theory. The quantum mechanical spread of the wave function for the homogeneous mode on the sphere suppresses the creation of high energy particles as the scalar field rolls down the potential and bounces back. This leads to the prediction that a quantum transition from the big crunch to a big bang is the most probable outcome of cosmological evolution, for a specific parameter range. We briefly comment on cosmological perturbations.
1530h: Journal club discussion
Speaker: TBA
Friday May 9
(University of Amsterdam)
1400h: Seminar in room C.302
Speaker: Paolo Creminelli (ICTP, Trieste)
Title: The Effective Field Theory of Inflation and Quintessence
Abstract:
We study the effective field theory of inflation, i.e. the most general theory describing the fluctuations around a quasi de Sitter background, in the case of single field models. This approach allows us to characterize all the possible high energy corrections to simple slow-roll inflation, whose sizes are constrained by experiments. Also, it describes in a common language all single field models, including those with a small speed of sound and Ghost Inflation, and it makes explicit the implications of having a quasi de Sitter background. The non-linear realization of time diffeomorphisms forces correlation among different observables, like a reduced speed of sound and an enhanced level of non-Gaussianity. The same approach can be used to study the most general model of quintessence. We find that that there is no pathology in evolving to the region w < -1: the phantom divide does not exist. Stability constraints imply, for w < -1, a speed of sound very close to zero.
1530h: Journal club discussion in ITP lounge
Speaker: Balt van Rees (ITP Amsterdam)
Balt will discuss his recent paper
"Real-time gauge/gravity duality" with K. Skenderis [hep-th:0805.0150]