Thermodynamics of light emission

TL;DR

This paper introduces a thermodynamic framework for analyzing the irreversibility of light emission processes by associating an entropy to electromagnetic fields, bridging classical and quantum descriptions.

Contribution

It proposes a novel entropy measure for electromagnetic fields based on diagonal entropy, linking quantum statistical mechanics with thermodynamics of light emission.

Findings

Quantifies irreversibility in light emission processes.

Provides a thermodynamic interpretation of electromagnetic field interactions.

Applies to both classical and quantum descriptions of light.

Abstract

Some interactions between classical or quantum fields and matter are known to be irreversible processes. Here we associate an entropy to the electromagnetic field from well-known notions of statistical quantum mechanics, in particular the notion of diagonal entropy. We base our work on the study of spontaneous emission and light diffusion. We obtain a quantity which allows to quantify irreversibility for a quantum and classical description of the electromagnetic field, that we can study and interpret from a thermodynamical point of view.