On long range axion hairs for black holes

Abstract

The physics of black holes can suggest new ways to test the existence of axions. Much work has been done so far to analyse the phenomenon of superradiance associated with axions in the ergoregion surrounding rotating black holes. In this work, we instead investigate how Chern-Simons axion couplings of the form $\varphi F\tilde{F}$ and $\varphi R\tilde{R}$, well motivated by particle physics and string theory, can induce long range profiles for light axion fields around charged black holes, with or without spin. We extend known solutions describing axion hairs around spherically symmetric, asymptotically flat dyonic black hole configurations, charged under $U(1)$ gauge symmetries, by including non-minimal couplings with gravity. The axion acquires a profile controlled by the black hole conserved charges, and we analytically determine how it influences the black hole horizon and its properties. We find a Smarr formula applying to our configurations. We then generalise known solutions describing axion hairs around slowly rotating black hole configurations with charge. To make contact with phenomenology, we briefly study how long range axion profiles induce polarised deflection of light rays, and the properties of ISCOs for the black hole configurations we investigate.

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Cited by in corpus (9)

• Black holes with scalar hair in light of the Event Horizon Telescope
• Charged black holes with axionic-type couplings: classes of solutions and dynamical scalarisation
• Compact objects with primary hair in shift and parity symmetric beyond Horndeski gravities
• Spinning Black Holes with Axion Hair
• Novel exact ultra-compact and ultra-sparse hairy black holes emanating from regular and phantom scalar fields
• Analytic and asymptotically flat hairy (ultra-compact) black-hole solutions and their axial perturbations
• Probing the signature of axions through the quasinormal modes of black holes
• Hairy black holes in extended Einstein-Maxwell-scalar theories with magnetic charge and kinetic couplings
• Linear perturbations of dyonic black holes in the lowest-order $U(1)$ gauge-invariant scalar-vector-tensor theories