Quest for particles production in the plane gravitational wave spacetime

TL;DR

This paper derives Green's functions for massless fields in a plane gravitational wave spacetime, showing no particle production occurs, and compares different theoretical approaches to this phenomenon.

Contribution

It provides exact Green's functions using three methods and clarifies the absence of massless particle creation in this specific gravitational background.

Findings

Green's functions obtained in closed form

No massless particle production in plane gravitational wave spacetime

Different methods yield consistent results

Abstract

Massless vector and scalar Green's functions are obtained in closed form for a plane gravitational wave spacetime using three independent methods: direct solution of the Green-function equation and construction via the DeWitt and Hadamard recursive schemes. The results coincide exactly with the DeWitt--Schwinger expansion, indicating no massless particles production in this background. Contrasting interpretations, based on Bogolyubov coefficient calculations predicting massless particle creation, are also addressed.