Cosmology & Gravitation

This series consists of talks in the areas of Cosmology, Gravitation and Particle Physics.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

 

Tuesday Sep 29, 2009
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Near the Planckian scales, quantum gravity is expected to drastically change the structure of spacetime, one feature of which may be noncomutativity of the coordinates. Based on the recent advances in
quantum field theories on such noncommutative spaces, I will consider the
fluctuations of inflaton and look for possible noncommutative corrections
in the CMB. Anisotropy and non-gaussianity are the result. The resultant
distribution is then compared with ACBAR, CBI and WMAP data to constrain
the scale of noncommutativity parameter.

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Thursday Sep 24, 2009
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I describe a number of techniques that allow for the generation of (near) scale-invariant fluctuations in the early Universe without inflation or ekpyrosis. The basic ingredient is a decaying maximal speed of propagation, for which a Universal law is found. Connections are made with k-essence, the cuscaton, and the DBI action. However the simplest realizations result from bimetric theories and deformed dispersion relations and DSR. A number of implications to theories of quantum gravity are discussed.

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Tuesday Sep 22, 2009
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In addition to its ability to probe Inflation, CMB polarization offers the intriguing possibility to detect CP-symmetry violation. In some sense these predictions, if true, would be more surprising than confirmation of the inflationary paradigm -- for which ample, albeit circumstantial, evidence already exists. Moreover, recent theoretical predictions imply that, not only are parity violating CMB polarization effects possible, but that they have already been detected at 3\sigma confidence levels in existing polarization data.

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Tuesday Sep 08, 2009
Speaker(s): 

The standard model of cosmology has some puzzles/problems such as the
cosmological constant problem and the horizon problem which according to
many stem from our lack of understanding of the very early universe. This in turn means that almost none of the theories of quantum gravity are at a
stage where anything substantial can be said about observational cosmology.
In the past few years Causal Set theory has proved itself different in this
case where a possible solution to the Cosmological constant problem was

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Tuesday Sep 01, 2009
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We present the first year SDSS-II Supernova Survey results and their implications for cosmology and future supernova surveys. We then discuss challenges that face next-generation surveys, such as LSST, which will deliver of order a million supernovae without spectroscopic confirmation. As a way to address these challenges, we introduce BEAMS, a statistical method to do photometric supernova cosmology, and present a preliminary application to SDSS data.

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