Speaker
Description
In the first part I discuss the evolution of entanglement entropy for a massless field within a spherical region in an expanding background. The formalism is applied to the inflationary period and the subsequent era of radiation domination, starting from the Bunch-Davies vacuum. Each field mode evolves towards a squeezed state upon horizon exit during inflation, with additional squeezing when radiation domination sets in. This results in the enhancement of the entanglement entropy. A volume term develops in the radiation-dominated era, and becomes the leading contribution to the entanglement entropy at late times. In the second part I discuss the form of the entanglement entropy in various gravitational backgrounds (de Sitter and anti-de Sitter space, the Einstein universe) focusing on the structure of the divergences. Universal coefficients are determined for ultraviolet and infrared divergent terms. A remarkable conclusion is that the entanglement entropy of sub-horizon regions in de Sitter space displays a logarithmic dependence on the size of the total system, which may extend beyond the horizon. In the third part I discuss the use of the finite part of the entropy for the calculation of c- and a-functions.
