How do CPT-like symmetries shape the stability of geophysical flows?

TL;DR

This paper explores how discrete symmetries like time-reversal and mirror symmetries influence the stability and dynamics of geophysical flows, revealing connections to concepts like PT symmetry and symmetry breaking.

Contribution

It develops a general framework linking real-space symmetries to Fourier-space and uncovers how symmetry breaking affects geophysical wave stability.

Findings

Baroclinic instability as PT symmetry breaking

Parity symmetry analogous to charge-conjugation-parity in fluids

Symmetry breaking suppresses wave propagation and can induce instability without breaking symmetry

Abstract

We examine the role discrete symmetries, time-reversal and mirror symmetries, play in the context of geophysical waves and instabilities. By looking at three special cases from the two-layer quasi-geostrophic model as well as developing a general framework for translating real-space transformations to Fourier-space we are able to: 1) show that baroclinic instability is an example of spontaneous parity-time symmetry breaking; 2) show that pure parity symmetry for a fluid system is exactly analogous to charge-conjugation-parity symmetry in a condensed matter system; and 3) show that when a pure parity symmetry is broken, this is associated with the suppression of wave propagation. Further, in the latter case, instability can arise without a corresponding symmetry breaking. This study highlights the role of symmetry breaking behind the dynamics of geophysical waves and instabilities.