Speaker
Description
De Sitter spacetime describes both the earliest and latest stages of our Universe, but its lack of time-translation symmetry means that many of the standard tools of quantum field theory do not directly apply. In this talk, I will introduce the in-in formalism as a framework for studying quantum fields in this setting and use it to investigate a stochastic version of the Schwinger effect. Focusing on massless QED in a fixed de Sitter background, relevant to Standard Model matter before electroweak symmetry breaking, I exploit conformal flatness to relate the problem to flat-space QED and study particle production induced by a de Sitter-invariant stochastic electromagnetic field. Along the way, I will discuss the physical picture behind the mechanism, the challenges that arise in curved spacetime, and some open questions for extending the approach beyond the massless and exactly de Sitter limits.