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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 Aug 01, 2017
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In 1977, Blandford and Znajek  discovered a process by which a spinning 

black hole can transfer rotational energy to a force-free plasma, offering a possible mechanism for energy and jet emissions from quasars and other astrophysical sources.  This Blandford-Znajek (BZ) mechanism is a Penrose process, which exploits the presence of an ergosphere supporting negative energy states, and it involves currents of electrical charge sourcing the toroidal  magnetic field component of the emitted Poynting flux.  

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Tuesday Jul 25, 2017
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We present an analytic, perturbative solution that describes dynamical black holes in slow-roll inflation with a general potential.

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Monday Jul 17, 2017
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One of the basic puzzles of black hole thermodynamics is the simplicity and universality of the  Bekenstein-Hawking entropy.

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Tuesday May 30, 2017

The Lambda Cold Dark Matter framework successfully accounts for observational constraints on large (> 1 Mpc) scales, from the clustering of galaxies to the angular dependence of the Cosmic Microwave Background to the structure and matter content of galaxy clusters. On the scale of individual galaxies and, in particular, of dwarf systems much fainter than the Milky Way, a number of apparent conflicts with LCDM expectations have been reported.

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Tuesday May 23, 2017
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The first phase of stellar evolution in the history of the Universe may be Dark Stars (DS), powered by dark matter heating rather than by nuclear fusion. Weakly Interacting Massive Particles, which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel, with lifetimes from millions to billions of years.

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Tuesday May 16, 2017
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Fast Radio Bursts are mysterious radio flashes that appear to have extragalactic origin. The inferred isotropic brightness temperature for these events can exceed 10^34 K. Discovered in 2006, only about 25 have been reported to date.

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Thursday May 11, 2017

Gravitational lensing is one of the primary investigation tools of all current and future wide field surveys. In this talk I will review its current status (with the Kilo Degree Survey (KiDS)) and show what unique cosmological information it gives us. Lensing is not limited to a, low redshift, dark universe probe, it can also be used as a tool to probe baryons and nicely work in synergy with baryonic probes (e.g. CMB, Xray, tSZ, HI). I will show some of the work in progress to help constraining Active Galactic Nuclei feedback

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Tuesday Apr 11, 2017
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A number of ground based CMB surveys that will survey large fractions of the sky to high sensitivity are currently in the planning stages.  I will give an overview of what can be learned from these surveys about the Universe since recombination, focussing on gravitational lensing science.  I will also discuss some new CMB observables that would be accessible with even more futuristic surveys.

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Tuesday Mar 28, 2017

Cosmology has seen great progress thanks to precision measurements and is bound to greatly benefit from upcoming Large Scale Structure and Cosmic Microwave Background data. I will point out a number of interesting directions. In particular, I discuss how the microphysics of inflation may be tested in galaxy surveys through “fossil” signatures originating from squeezed primordial correlations.

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Tuesday Mar 21, 2017
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I will describe the Dark Energy Spectroscopic Instrument (DESI), an instrument currently being built to carry out a large galaxy redshift survey.  DESI is the next step beyond the SDSS and BOSS surveys, mapping over 30 million galaxies.  I will focus in particular on the amazing engineering challenges of the DESI instrument itself, which includes a 5,000-robot army and 250 kilometers of fiber optics.  I will conclude by briefly describing the work I am personally involved in: a large imaging survey that will measure the galaxies from which DESI will select targets for

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