The Effect of Gravitational Tidal Forces on Vacuum Polarization: How to Undress a Photon

TL;DR

This paper explores how gravitational tidal forces influence photon behavior in curved spacetime, revealing effects like amplification and attenuation linked to virtual particle clouds, with implications near black holes.

Contribution

It introduces a novel analysis of tidal forces affecting photon dressing and undressing, connecting local refractive index variations to virtual particle cloud dynamics in curved spacetime.

Findings

Im n(u;w) can be negative or positive, indicating amplification or attenuation.

Photon undressing occurs near black hole singularities.

Results align with unitarity and the optical theorem in curved spacetime.

Abstract

The effect of gravitational tidal forces on photon propagation in curved spacetime is investigated. It is found that the imaginary part of the local refractive index Im n(u;w) may be negative as well as positive, corresponding to a local amplification as well as attenuation of the amplitude of the renormalized photon field. This is interpreted in terms of the effect of tidal forces on the virtual e^+e^- cloud surrounding the bare photon field---a positive/negative Im n(u;w) corresponds to an increased dressing/undressing of the bare photon. Below threshold decays of the photon to e^+e^- pairs can occur. Photon undressing in the vicinity of a black hole singularity is described as an example. These results are shown to be consistent with unitarity and the optical theorem in curved spacetime, which is derived here both in a local form and integrated over the photon trajectory.