Speaker
Description
Title: Complex metrics and the no-boundary wave function
Abstract: I will provide an introduction to the no-boundary wave function, and review its implementation in simple inflationary models. Earlier treatments indicated that the no-boundary wave function would favour very short inflationary phases, in strong tension with observations. Recent investigations have shown the need for a more careful definition, especially with regards to the question of which metrics and field configurations should be summed over in gravitational path integrals. This leads both to a deeper understanding of gravitational path integrals, and to the consequence that, under certain circumstances, long inflationary phases are required. I will discuss the implications for observational predictions, in particular for the size of the universe, and I will comment on the relation to string theory.
