2025/07/08 by Lazarte, Claudio, Sanchis-Gual, Nicolas, Font, José A. +1
#FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc)
paper · doi:10.48550/arxiv.2507.06145
Vector boson stars, also known as Proca stars, exhibit remarkable dynamical robustness, making them strong candidates for potential astrophysical exotic compact objects. In search of theoretically well-motivated Proca star models, we recently introduced the ℓ-Proca star, a multi-field extension of the spherical Proca star, whose (2ℓ + 1) constitutive fields have the same time and radial dependence, and their angular structure is given by all the available spherical harmonics for a fixed angular momentum number ℓ. In this work, we conduct a non-linear stability analysis of these stars by numerically solving the Einstein-(multi, complex) Proca system for the case of ℓ = 2, which are formed by five constitutive independent, complex Proca fields with m = 0, |1|, and |2|. Our analysis is based on long-term, fully non-linear, 3-dimensional numerical-relativity simulations without imposing any symmetry. We find that (ℓ=2)-Proca stars are unstable throughout their entire domain of existence. In particular, we highlight that less compact configurations dynamically lose their global spherical symmetry, developing a non-axisymmetric m=4 mode instability and a subsequent migration into a new kind of multi-field Proca star formed by fields with different angular momentum number, ℓ=1 and ℓ=2, that we identify as unstable multi-ℓ Proca stars.