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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.

## Hawking Radiation Energy and Entropy from a Bianchi-Smerlak Semiclassical Black Hole

Mardi juil 14, 2015
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Eugenio Bianchi and Matteo Smerlak have found a beautiful relationship between the Hawking radiation energy and von Neumann entropy in a conformal field emitted by a semiclassical two-dimensional black hole. Shohreh Abdolrahimi and I compared this relationship with what might be expected for unitary evolution of a quantum black hole in four and higher dimensions.

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## Anamorphic cosmology

Mardi juin 02, 2015
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I will present a novel approach to explain the smoothness and flatness of the universe on large scales and the generation of a nearly scale-invariant spectrum of adiabatic density perturbations.

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## Cross correlations with CMB secondaries: constraining cosmological parameters and cluster astrophysics.

Mardi avr 28, 2015
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High resolution CMB experiments, such as ACT, SPT, and the Planck satellite are making precision measurements of the secondary anisotropies caused by the thermal Sunyaev Zel'dovich (tSZ) effect from galaxy clusters. However, our ability to obtain cosmological information from this tSZ signal is limited by our theoretical understanding of the baryons in clusters and groups. I will discuss how cross correlation methods are providing new windows into the messy “Gastrophysics” of the intracluster medium and the potential for these methods to constrain various cosmological parameters.

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## Symbolic dynamics, modular curves, and Bianchi IX cosmologies

Jeudi avr 23, 2015
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## Cosmic ray feedback in galaxies and cool core clusters

Mardi avr 21, 2015
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Understanding the physics of galaxy formation is arguably among the greatest problems in modern astrophysics. Recent cosmological simulations have demonstrated that "feedback" by star formation, supernovae and active galactic nuclei appears to be critical in obtaining realistic disk galaxies, to slow down star formation to the small observed rates, to move gas and metals out of galaxies into the intergalactic medium, and to balance radiative cooling of the low-entropy gas at the centers of galaxy clusters.

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## Inference of weak gravitational lensing signals from sky images

Mardi avr 14, 2015
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Weak gravitational lensing is a highly valued tool for inferring the structure of the spacetime metric between an observer and a cosmologically distant “wallpaper,” most commonly either the CMB or faint background galaxies.

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## Symmetries in large scale structure

Lundi avr 13, 2015
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## From precision to accuracy: cosmology with large imaging surveys

Mardi avr 07, 2015
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Photometric surveys are often larger and extend to fainter magnitudes than spectroscopic samples, and can therefore yield more precise cosmological measurements. However, photometric data are significantly contaminated by multiple sources of systematics, either intrinsic, observational, or instrumental. These systematics affect the properties of the raw images in complex ways, propagate into the final catalogues, and create spurious spatial correlations.

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## Approaches to tests of gravity on cosmological scales

Mardi mar 31, 2015

More than a decade after its discovery, cosmic acceleration still
poses a puzzle for modern cosmology and a plethora of models of dark energy
or modified gravity, able to reproduce the observed expansion history, have
been proposed as alternatives to the cosmological standard model. In recent
years it has become increasingly evident that probes of the expansion his-
tory are not sufficient to distinguish among the candidate models, and that
it is necessary to combine those with observations that probe the dynamics

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## Anthropic Origin of the Neutrino Mass from Cooling Failure

Mardi mar 24, 2015
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Given a large landscape of vacua that statistically favors large values of the neutrino mass sum, $m_\nu$, I will present the probability distribution over $m_\nu$ obtained by weighting this prior by the amount of galaxies that are produced. Using Boltzmann codes to compute the smoothed density contrast on Mpc scales, we find that large dark matter halos form abundantly for $m_\nu \gtrsim 10$\,eV. However, in this regime structure forms late and is dominated by cluster scales, as in a top-down scenario.

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## RECENT PUBLIC LECTURE

### Art McDonald: A Deeper Understanding of the Universe from 2 km Underground

Speaker: Arthur B McDonald