Ben Craps, Vrije Universiteit Brussel and
The International Solvay Institutes, Belgium
"Quantum resolution of cosmological singularities using AdS/CFT"
ABSTRACT:
Despite impressive phenomenological successes, cosmological models are
incomplete without an understanding of what happened at the big bang
singularity. Depending on the model, one would like to understand how
appropriate “initial conditions” were selected at the big bang
singularity, or how a pre-existing contracting universe underwent a
big crunch/big bang transition, if such transitions are possible at
all. In this talk, based on work with T. Hertog and N. Turok, I
discuss a five-dimensional model cosmology with a big crunch
singularity and ask whether time evolution can be consistently defined
beyond this singularity, which would then be the big bang of an
expanding universe. We use the AdS/CFT correspondence to map the
problem to the study of a dual quantum field theory with a potential
unbounded below, where the singularity corresponds to a field reaching
infinity in finite time. The main idea is to use “self-adjoint
extensions”, which amounts to putting boundary conditions at infinity
in field space. Our results suggest that, at least in a certain
parameter regime, a big crunch/big bang transition is the most likely
outcome of cosmological evolution. We end with some speculations on
the generation of nearly scale invariant cosmological perturbations.
