# Thermal Emission from Semi-classical Dynamical Systems

## TL;DR

This paper explores how quantum corrections in semi-classical dynamical systems can induce thermal emission, potentially saturating the chaos bound even in integrable models, and relates this to acoustic Hawking radiation.

## Contribution

It demonstrates that quantum effects can cause thermal emission in classical-like systems and discusses conditions under which the chaos bound is saturated.

## Key findings

- Quantum corrections induce Boltzmann-distributed energy emission.
- Emission is related to acoustic Hawking radiation.
- Certain integrable models may saturate the chaos bound.

## Abstract

Recently the bound on the Lyapunov exponent $\lambda_L \le 2\pi T/ \hbar$ in thermal quantum systems was conjectured by Maldacena, Shenker, and Stanford. If we naively apply this bound to a system with a fixed Lyapunov exponent $\lambda_L$, it might predict the existence of the lower bound on temperature $T \ge \hbar \lambda_L/ 2\pi $. Particularly, it might mean that chaotic systems cannot be zero temperature quantum mechanically. Even classical dynamical systems, which are deterministic, might exhibit thermal behaviors once we turn on quantum corrections. We elaborate this possibility by investigating semi-classical particle motions near the hyperbolic fixed point and show that indeed quantum corrections may induce energy emission which obeys a Boltzmann distribution. We also argue that this emission is related to acoustic Hawking radiation in quantum fluid. Besides, we discuss when the bound is saturated and show that a particle motion in an inverse harmonic potential and $c=1$ matrix model may saturate the bound although they are integrable.