Status  Confirmed 
Seminar Series  STRLPTENSHE 
Subjects  hepth 
Date  Friday 4 December 2020 
Time  14:00 
Institute  LPTENS 
Seminar Room  GoToMeeting 
Speaker's Last Name  Le Floch 
Speaker's First Name  Bruno 
Speaker's Email Address  
Speaker's Institution  Institut Philippe Meyer 
Title  Universal scattering laws for quiescent bouncing cosmology 
Abstract  Modifications to 3+1d general relativity (GR) at high curvatures can eliminate the Big Bang singularity in favor of a bounce. Abstracting away microscopic details of the bounce, the spacetime is simply a GR solution on both sides of a singularity hypersurface, with some theorydependent "singularity scattering map" relating the asymptotic metrics on both sides. The asymptotic metric near a singularity was studied by Belinsky, Khalatnikov and Lifshitz (BKL) and I will explain their finding that the time evolution at different points decouples. Motivated by this ultralocality property, we classify (in the absence of BKL oscillations) all singularity scattering maps that are ultralocal. By matching previous calculations on homogeneous spacetimes in f(R) gravity and in loop quantum cosmology with our classification we obtain a prediction for nonhomogeneous bounces in these theories. Lastly, we construct a class of cyclic spacetimes by solving for the collision of plane gravitational waves (which may create infinitely many successive singularities). 
arXiv Preprint Number  2006.08620 
Comments  Connection details posted somewhat soon 
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