Title: NONSINGULARBOUNCING COSMOLOGY IN GENERAL RELATIVITY.

Speaker: Emmanuele Battista, Institute for Theoretical Physics(ITP), Karlsruhe Institute of Technology (KIT)

Time:March 5,202116:00

Venue: 302，Physics Building

Onlinereport: https://cern.zoom.us/j/61689351926?pwd=M0FOZUpRME1RYUYxeWMvRyszbUQ1Zz09

Abstract：Spacetimedefect has been recently proposed in the literature as a tool to tame thebig-bang singularity. Such anobject can be described by a degenerate metric with a vanishing determinant ona 3-dimensional submanifold of the spacetime and a nonzero length scale b,which acts as a“regulator" of the Friedmann singularity. This new metrichas been called the regularized-big-bang metric and it gives rise to anonsingular spatially flat Friedmann-type solution of the Einsteingravitational field equation which allows for a“pre-big-bang" phase witha bounce-type behavior of the cosmic scale factor. In this talk, I willdescribe some features underlying this regularized geometry. In particular, Iwill discuss the physical effects pointing out the presence of the defect inthe regularized Robertson-Walker spacetime by considering two main physicalquantities: the compressive forces acting on (human) observers and the energypossessed by massive particles and photons during their dynamical evolution.