Seminar by Andrzej Krolak

Seminar by Andrzej Krolak

 

Strong curvature singularities 

- past and future

 

Time: 12:30 PM 

Date: March 23, 2017

Gravity Suite

 

Seminar by Lucas Fabian

Seminar by Lucas Fabian

Talk time and date:

March 21th at 11:00 AM in Nicholson 241

 

 

 

 

 

 

 

 

Title: Review / progress report on entanglement of squeezed vacua

Abstract: There is a lot of ongoing work using complex structures to study power spectrum and entanglement entropy of scalar perturbations in cosmology. I will review our general methods and explain the machinery connecting entanglement entropy, correlation function and complex structure for Gaussian states. There are some subtleties when going from finitely many degrees of freedom to infinitely many, due to unitarily inequivalent representations. A recent progress provided an elegant method of finding adiabatic vacua using an ε expansion of the complex structure, rather than going through the standard WKB approximation. This aspect is still incomplete, but I will explain the general approach.

Seminar by Lucas Fabian

Seminar by Lucas Fabian

Talk time and date:

March 20th at 1:30 AM in Nicholson 241

 

 

 

 

 

 

 

 

Title: Entanglement production at parametric resonance

Abstract: The most prominent example in cosmology is the reheating phase where one couples a test scalar matter field to the inflaton field treated as a classical source.  Our result is a generic theorem stating that the entanglement entropy associated to a detector grows linearly in time with a slope given by the Floquet exponents associated to resonant modes.

Seminar by Alec Yonika

 

 

Talk time and date:

Jan 11th at 11:30 AM in Nicholson 241

 

 

 

 

 

 

 

 

Title: Numerical Analysis of the Schwarzschild Interior

Abstract: Loop quantum cosmology (LQC) is a theory attempting to unite the fields of quantum theory and general relativity. In these unification attempts, LQC takes the continuous spacetime of general relativity and makes it discrete. This discretization yields some interesting results; namely, the emergence of finite-difference (FD) equations where partial difference equations usually present. FD equations present some opportunities for analysis that are not normally present. This opportunity is that of numerical analysis. Largely, numerical analysis of LQC schemes has been ignored. To rectify this, we present a method of analyzing LQC schemes. We take the example of the scheme presented in Corichi and Singh [1]. However, the methods presented herein may be used in the general case.

Talk by Wolfgang Wieland

Speaker: Wolfgang Wieland, Perimeter Institute
Place: 241 Nicholson
Date: Wednesday November 16th
Time: 11am

Title: Discrete Gravity as a topological field theory with defects






Abstract:
I give a proposal for discrete GR (as a field theory) in terms of self-dual variables. The manifold is spilt into four-dimensional regions, which are flat or constantly curved inside. The boundary of every such four-cell is a three-surface, which is taken to be null. The contribution to the action from the four-cells is trivial, only the internal three-boundaries and two-dimensional corners contribute non-trivially. Finding the right dynamics boils then down to finding the right boundary term. On a null surface, the natural such boundary term is built from a spinor and a spinor-valued two-form, which are canonically conjugate to each other. I discuss the relevance of the model for non-perturbative approaches to quantum gravity, such as loop quantum gravity, where similar variables have recently appeared as well. The talk is based on the paper: arXiv:1611.02784

Seminar by David Garfinkle

Talk time and date:

Nov 11th at 11 AM in Nicholson 241

Title: Spikes in the approach to spacetime singularities

Abstract: As a spacetime singularity is approached spatial structures develop on a small and ever shrinking spatial scale.  These structures are called spikes.  This talk will cover analytic approximations of spikes, numerical simulations of spikes, and the possibility that spikes might be destroyed by the effects of quantum gravity.

Seminar by Marios Christodoulou

  Talk time and date:
  Nov 8th at 11:30 in Nicholson 241

Title: Complete Observable from covariant LQG: The Planck Star Tunneling time

Abstract: 

Covariant LQG provides the machinery to define probability amplitudes for transitions between 3D geometries via a path integral over interpolating quantum spacetimes. An astrophysically relevant probability is expected for the transition of a Black Hole to a White Hole geometry. The setup for this calculation provides a concrete example of how to use cov LQG and extract a complete observable from the theory and how to deal with the "problem of time".