New Structures in the Theory of the Laser Model

TL;DR

This paper extends the laser model by providing a microscopic perspective that reveals the dynamics are driven by a macroscopic field, the system's state becomes uncorrelated over time, and it maximizes entropy given current macroscopic constraints.

Contribution

It introduces a microscopic formulation of the laser model that complements existing macroscopic descriptions, highlighting the role of the macroscopic field and entropy maximization.

Findings

Microscopic dynamics are driven by the macroscopic field.

System states become uncorrelated after transients.

States maximize entropy density given macroscopic variables.

Abstract

In a recent article, Alli and Sewell formulated a new version of the Dicke-Hepp-Lieb laser model in terms of quantum dynamical semigroups, and thereby extended the macroscopic picture of the model. In the present article, we complement that picture with a corresponding microscopic one, which carries the following new results. (a) The local microscopic dynamics of the model is piloted by the classical, macroscopic field, generated by the collective action of its components; (b) the global state of the system carries no correlations between its constituent atoms after transient effects have died out; and (c) in the latter situation, the state of the system at any time $t$ maximises its entropy density, subject to the constraints imposed by the instantaneous values of its macroscopic variables.