Catastrophe Structure and Stability of Axion Stars
Abstract
Axion stars are self-gravitating Bose--Einstein condensates of QCD axions or axion-like particles. Their stability determines whether they can survive as dark-matter structures and what astrophysical signatures they may produce. Here we combine a non-relativistic Schrödinger--Poisson description with catastrophe theory to develop a unified picture of axion-star stability. Beginning with the Einstein--Klein--Gordon system for a periodic axion potential, we derive the effective equations of motion and conserved quantities and construct a one-parameter family of star-like solutions. A Gaussian variational ansatz reduces the problem to an analytic energy functional E(R;N). Within this model, equilibria appear and disappear through Arnold A2, A3, and A4 catastrophes as the particle number N and interaction strengths vary. A repulsive sextic interaction produces two stable branches---dilute and dense axion stars---separated by an unstable branch. The same catastrophe criteria apply beyond the sextic truncation: for the full cosine and QCD-corrected potentials, the fold conditions follow from the complete variational energy and can be evaluated numerically. We also separate stability within the collective-coordinate ansatz from full radial perturbative stability and specify the range in which the non-relativistic treatment is reliable. This framework provides a compact classification of axion-star phases and identifies model-dependent critical masses associated with collapse, bosenova-like emission, and black-hole formation.
Related
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- Effects of axion interactions on quark stars in 4D Einstein–Gauss–Bonnet gravity
- Nonradial oscillation modes of axion condensed neutron stars in the Cowling approximation
- Axion-angle dependence of the rotational and tidal properties of PNJL quark stars
- Axion effects on hybrid stars: earlier hadron-quark phase transition and larger quark-matter cores
BibTeX
@misc{kusmartsev2026catastrophe,
title = {{Catastrophe Structure and Stability of Axion Stars}},
author = {Fedor V Kusmartsev and Joudy J F Beek and Jack C M Hughes},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.33549},
eprint = {2610.33549},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.33549},
note = {CC0},
}
RIS
TY - UNPB
TI - Catastrophe Structure and Stability of Axion Stars
AU - Fedor V Kusmartsev
AU - Joudy J F Beek
AU - Jack C M Hughes
PY - 2026
DA - 2026/10/24
PB - arXiv
DO - 10.48550/arxiv.2610.33549
UR - https://arxiv.org/abs/2610.33549
AB - Axion stars are self-gravitating Bose--Einstein condensates of QCD axions or axion-like particles. Their stability determines whether they can survive as dark-matter structures and what astrophysical signatures they may produce. Here we combine a non-relativistic Schrödinger--Poisson description with catastrophe theory to develop a unified picture of axion-star stability. Beginning with the Einstein--Klein--Gordon system for a periodic axion potential, we derive the effective equations of motion and conserved quantities and construct a one-parameter family of star-like solutions. A Gaussian variational ansatz reduces the problem to an analytic energy functional E(R;N). Within this model, equilibria appear and disappear through Arnold A_2, A_3, and A_4 catastrophes as the particle number N and interaction strengths vary. A repulsive sextic interaction produces two stable branches---dilute and dense axion stars---separated by an unstable branch. The same catastrophe criteria apply beyond the sextic truncation: for the full cosine and QCD-corrected potentials, the fold conditions follow from the complete variational energy and can be evaluated numerically. We also separate stability within the collective-coordinate ansatz from full radial perturbative stability and specify the range in which the non-relativistic treatment is reliable. This framework provides a compact classification of axion-star phases and identifies model-dependent critical masses associated with collapse, bosenova-like emission, and black-hole formation.
ER -