Wightman function and stochastic gravity noise kernel in impulsive plane wave spacetimes

TL;DR

This paper investigates quantum field behavior and stochastic gravity noise in impulsive plane wave spacetimes, analyzing geodesics, singularity structures, and the noise kernel's properties near conjugate planes.

Contribution

It provides a detailed analysis of the Wightman function and noise kernel in impulsive plane wave spacetimes, highlighting their singularity structures and behavior near conjugate planes.

Findings

Wightman function exhibits twofold and fourfold singularities crossing conjugate planes.

Explicit form of the stochastic gravity noise kernel is derived in terms of world function and Van Vleck determinant.

Singularity structure of the noise kernel changes near the lightcone when crossing conjugate planes.

Abstract

In this paper we study quantum field theory in impulsive plane wave spacetimes. We first analyze the geodesics and the formation of conjugate planes in these spacetimes. The behaviors of the world function and the van Vleck determinant near conjugate plane are also considered. For the quantum field, we work out the mode functions, their Bogoliubov transformations, and the construction of the Wightman functions. By examining the Wightman function near and on the conjugate plane, we show how the twofold and fourfold singularity structure of the Wigthman function arise when crossing this plane. Lastly, we come to the stochastic gravity noise kernel which is also the correlation function of the stress energy tensor of the quantum field. Its explicit form is given in terms of the world function and the van Vleck determinant. We investigate its limits for small and large geodesic distances. The leading divergent term of the noise kernel on the conjugate plane are expressed in terms of derivatives of delta functions. Similar to that of the Wightman functions, we also examine how the singularity structure of the noise kernel near the lightcone changes when crossing the conjugate plane.