Negative Temperature States in the Discrete Nonlinear Schroedinger Equation

TL;DR

This paper investigates negative temperature states in the discrete nonlinear Schrödinger equation, revealing metastable states with finite breathers density that can be experimentally realized and exhibit extremely slow convergence to equilibrium.

Contribution

It identifies and characterizes negative temperature states in the discrete nonlinear Schrödinger equation, including their formation, metastability, and experimental generation methods.

Findings

Negative temperature states exist in the system.

Convergence to equilibrium is extremely slow due to coarsening.

Negative temperature states can be experimentally generated.

Abstract

We explore the statistical behavior of the discrete nonlinear Schroedinger equation. We find a parameter region where the system evolves towards a state characterized by a finite density of breathers and a negative temperature. Such a state is metastable but the convergence to equilibrium occurs on astronomical time scales and becomes increasingly slower as a result of a coarsening processes. Stationary negative-temperature states can be experimentally generated via boundary dissipation or from free expansions of wave packets initially at positive temperature equilibrium.