String Pair Production in a Time-Dependent Gravitational Field

TL;DR

This paper investigates how string and point-particle pairs are produced in a weak, time-dependent gravitational field, revealing significant differences for massive string states with implications for cosmology and black hole physics.

Contribution

It introduces a method using string perturbation theory to compare pair production of strings and particles in weak gravitational backgrounds, highlighting novel differences for massive states.

Findings

String and point-particle pair production differ significantly for massive states.

Explicit calculations for arbitrary excitation levels of strings.

Potential implications for cosmology and black hole physics.

Abstract

We study the pair creation of point-particles and strings in a time-dependent, weak gravitational field. We find that, for massive string states, there are surprising and significant differences between the string and point-particle results. Central to our approach is the fact that a weakly curved spacetime can be represented by a coherent state of gravitons, and therefore we employ standard techniques in string perturbation theory. String and point-particle pairs are created through tree-level interactions between the background gravitons. In particular, we focus on the production of excited string states and perform explicit calculations of the production of a set of string states of arbitrary excitation level. The differences between the string and point-particle results may contain important lessons for the pair production of strings in the strong gravitational fields of interest in cosmology and black hole physics.