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  • Letter
  • Open Access

Exceptional ring of the buoyancy instability in stars

Armand Leclerc1,*, Lucien Jezequel2, Nicolas Perez1, Asmita Bhandare1, Guillaume Laibe1,3,†, and Pierre Delplace2

  • 1Univ. Lyon, Univ. Lyon 1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis,-Laval, France
  • 2Ens de Lyon, CNRS, Laboratoire de Physique, F-69342 Lyon, France
  • 3Institut Universitaire de France, France

  • *armand.leclerc@ens-lyon.fr
  • †guillaume.laibe@ens-lyon.fr
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Phys. Rev. Research 6, L012055 – Published 11 March, 2024

DOI: https://doi.org/10.1103/PhysRevResearch.6.L012055

Abstract

We reveal properties of global modes of linear buoyancy instability in stars, characterized by the celebrated Schwarzschild criterion, using non-Hermitian topology. We identify a ring of exceptional points of order 4 that originates from the pseudo-Hermitian and pseudochiral symmetries of the system. The ring results from the merging of a dipole of degeneracy points in the Hermitian stably-stratified counterpart of the problem. Its existence is related to spherically symmetric unstable modes. We obtain the conditions for which convection grows over such radial modes. Those are met at early stages of low-mass stars formation. We finally show that a topological wave is robust to the presence of convective regions by reporting the presence of a mode transiting between the wavebands in the non-Hermitian problem, strengthening their relevance for asteroseismology.

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Phys. Rev. Research 6, L012055– Published 11 March, 2024
  • Received 25 April 2023
  • Accepted 9 November 2023
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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