Worldline instantons for nonperturbative particle production by space and time dependent gravitational fields

TL;DR

This paper introduces a worldline-instanton method to compute the momentum spectrum of particles generated by gravitational fields varying in space and time, providing a new analytical tool for nonperturbative particle production analysis.

Contribution

The paper develops a novel worldline-instanton approach specifically for gravitational fields with space-time dependence, extending previous methods to more complex scenarios.

Findings

Provides a framework for calculating particle spectra in complex gravitational backgrounds

Describes the structure of instantons with complex middle parts and asymptotic trajectories

Lays groundwork for future quantitative studies of particle production in dynamic spacetimes

Abstract

We develop a worldline-instanton approach for calculating the momentum spectrum of particles produced by gravitational fields which depend on both space and time. The instantons are open. The middle part is complex and describes the formation region, while the ends describe the trajectories of asymptotic particles.