Radiative processes in external gravitational fields

TL;DR

This paper explores how external gravitational fields enable forbidden radiative processes, providing a method to calculate transition probabilities for particles of any spin and analyzing the impact of dissipation on gravitational backgrounds.

Contribution

It introduces a generalized momentum approach to compute radiative processes in gravitational fields, applicable to any particle spin and gravitational configuration, including dissipation effects.

Findings

Transition probabilities are linear in metric deviation to leading order.

Dissipation can induce resonances affecting gravitational backgrounds.

Method applies to particles of any spin in external gravitational fields.

Abstract

Kinematically forbidden processes may be allowed in the presence of external gravitational fields. These ca be taken into account by introducing generalized particle momenta. The corresponding transition probabilities can then be calculated to all orders in the metric deviation from the field-free expressions by simply replacing the particle momenta with their generalized counterparts. The procedure applies to particles of any spin and to any gravitational fields. transition probabilities, emission power, and spectra are, to leading order, linear in the metric deviation. It is also shown how a small dissipation term in the particle wave equations can trigger a strong backreaction that introduces resonances in the radiative process and deeply affects the resulting gravitational background.