ITP |
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Teilchentee SS 2018
Seminar at the Institute for Theoretical Physics, Heidelberg University
on Thursdays, 4 pm
organizers: Astrid Eichhorn, Jan M. Pawlowski
Before each seminar, the speaker gives an informal Pre-Talk, introducing the MSc and PhD students at the ITP to the broader context of the topic of the seminar.
Pre-Talks start at 3:30 pm
Date: 3.5.2018
Speaker: Jean-Luc Lehners (MPI Golm)
Title: Towards a quantum theory of the early universe
Abstract
The celebrated singularity theorems of Penrose and Hawking imply that classically our universe had a singularity in its past. This breakdown of general relativity is a clear sign that we need a more complete theory in order to understand the big bang and the purported beginning of our universe – in particular it is expected on general grounds that we will need a theory of quantum gravity. Finding a full theory of quantum gravity has however proven rather difficult. In this talk, I want to illustrate what we can learn about the early universe, and the big bang in particular, by using the tools already at our disposal, namely by using semi-classical gravity in the path integral formalism. This allows one to assess theories of initial conditions, such as the no-boundary proposal of Hartle and Hawking, which was proposed as a replacement of the big bang. It also allows us to investigate under what circumstances one can, and more interestingly when one cannot, describe the universe using quantum field theory in curved spacetime. Finally, the semi-classical approach hints at the existence of quantum transitions across the big bang, into an earlier phase of evolution.
