One thing that general relativity says about photons in matter

TL;DR

This paper explores the classical analogy of photons in dielectric media within general relativity, highlighting the limitations of quantum theory outside its framework and emphasizing the importance of homogeneity for such analogies.

Contribution

It combines historical and theoretical results to clarify when a quantum photon in a dielectric can be modeled classically, focusing on the role of homogeneity.

Findings

Quantum photons in dielectrics have classical analogs only if the dielectric is homogeneous.

Effective metrics can simplify electromagnetic problems in dielectrics.

Historical models provide insights into photon behavior in curved spacetime.

Abstract

Let us abandon for a moment the strict epistemological standpoint of quantum field theory, that eventually comes to declare nonsensical any question about the photon posed outside the quantum theoretical framework. We can then avail of the works by Whittaker et al. and by Synge about the particle and the wave model of the photon in the vacuum of general relativity. We can also rely on important results found by Gordon and by Pham Mau Quan: thanks to Gordon's discovery of an effective metric these authors have been able to reduce to the vacuum case several problems of the electromagnetic theory of dielectrics. The joint use of these old findings allows one to conclude that a quantum theoretical photon in an isotropic dielectric has a classical simile only if the dielectric is also homogeneous.