Unstable no-boundary fluctuations from sums over regular metrics.

by Alice Di Tucci (Max Planck Inst. for Gravitational Physics)

Monday 2 Jul 2018, 15:00 → 16:00 Europe/Rome

Sala Direzione (Sezione di Roma INFN)

It was recently shown by Feldbrugge et al. that the no-boundary proposal, defined via a Lorentzian path integral and in minisuperspace, leads to unstable fluctuations, in disagreement with early universe observations. In these calculations many off-shell geometries summed over in the path integral in fact contain singularities, and the question arose whether the instability might ultimately be caused by these off-shell singularities. We address this question here by considering a sum over purely regular geometries, by extending a calculation pioneered by Halliwell and Louko.