Kelvin-Helmholtz instability is the result of parity-time symmetry breaking

TL;DR

This paper reveals that Kelvin-Helmholtz instability arises from spontaneous PT-symmetry breaking in classical fluid systems, suggesting a universal mechanism for classical instabilities rooted in PT-symmetry principles.

Contribution

It demonstrates that classical fluid dynamics equations are PT-symmetric and links Kelvin-Helmholtz instability to PT-symmetry breaking, offering a new perspective on classical instabilities.

Findings

Kelvin-Helmholtz instability results from PT-symmetry breaking.

Classical fluid systems governed by Newton's law exhibit PT-symmetry.

PT-symmetry breaking is a generic mechanism for classical instabilities.

Abstract

Parity-Time (PT)-symmetry is being actively investigated as a fundamental property of observables in quantum physics. We show that the governing equations of the classical two-fluid interaction and the incompressible fluid system are PT-symmetric, and the well-known Kelvin-Helmholtz instability is the result of spontaneous PT-symmetry breaking. It is expected that all classical conservative systems governed by Newton's law admit PT-symmetry, and the spontaneous breaking thereof is a generic mechanism for classical instabilities. Discovering the PT-symmetry of systems in fluid dynamics and plasma physics and identifying the PT-symmetry breaking responsible for instabilities enable new techniques to classical physics and enrich the physics of PT-symmetry.