Speaker: Thomas Colas (Cambridge)
Title: Non-unitary effects in the early universe: dissipation and decoherence of cosmological inhomogeneities
Abstract: While multifield constructions are ubiquitous in the attempt of embedding inflation within a wider UV picture, cosmological data are consistent with the existence of a single scalar adiabatic degree of freedom. In order to describe the theory at the level of the observed degrees of freedom, one often has to integrate out unobserved sectors. On the top of a single-field effective action, this procedure also leads to non-unitary effects such as dissipation and decoherence that cannot be accounted for within a unitary description. I will present the Open Effective Field Theory approach which aims at incorporating these non-unitary effects in a systematic manner and discuss some situations where non-unitary effects might be significant.