de Sitter vacua in String Theory and $\alpha'$-corrected cosmology

by Dr Heliudson Bernardo (McGill University)

Monday 3 Feb 2020, 13:15 → 14:15 Europe/Stockholm

132:028 (Nordita East)

Recently, the existence of de Sitter string vacua have been discussed intensively. While there are effective 4 dimensional models that advocate the existence of such vacua, it is not totally clear how they could come from a full 10 dimensional calculation. On top of that some general arguments about string compactification were recently used to claim that dS vacua are not in the string landscape. I will discuss about these issues to motivate the need for a new framework for string cosmology. Then, I will present how a certain non-compact symmetry that appears once we consider purely time-dependent backgrounds can be used to classify all duality invariant $\alpha'$-corrections to the massless NS-NS sector of perturbative string theory. I will also show cosmological solutions for the resulting equations in presence of matter.