2015/03/31 by Tomi Koivisto, Hannu J. Nyrhinen · 9 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics #Black hole (networking) #Classical field theory #Classical mechanics #Cosmology and Gravitation Theories #Dark matter #Gravitation #Instability #Physics #Pulsars and Gravitational Waves Research #Quantum mechanics #Scalar (mathematics) #Scalar field #Scalar theories of gravitation #Theoretical physics #astro-ph.CO #gr-qc #hep-th
paper · pdf · doi:10.1088/1402-4896/aa85cc
published in Physica Scripta 92(10), 105301 (IOP Publishing) · 14 pages, 6 figures, abstract and introduction rewritten, typos corrected
arxiv created 2017/08/20 · openalex publication_date 2017/09/12 · arxiv updated 2017/09/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/08
The no-hair theorem postulates that the only externally observable properties of a black hole are its mass, its electric charge, and its angular momentum. In scalar-tensor theories of gravity, a matter distribution around a black hole can lead to the so called ‘spontaneous scalarisation’ instability that triggers the development of scalar hair. In the Brans–Dicke type theories, this effect can be understood as a result of tachyonic effective mass of the scalar field. Here we consider the instability in the generalised class of scalar-theories that feature non-conformal, i.e. ‘disformal’, couplings to matter. Such theories have gained considerable interest in the recent years and have been studied in a wide variety of systems, both cosmological and astrophysical. In view of the prospects of gravitational wave astronomy, it is relevant to explore the implications of the theories in the strong-gravity regime. In this article, we concentrate on the spontaneous scalarisation of matter configurations around Schwarzschild and Kerr black holes. We find that in the more generic scalar-tensor theories, the instability of the Brans–Dicke theory can be enhanced, suggesting violations of the no-hair theorem. On the other hand, we find that, especially if the coupling is very strong, or if the gradients in the matter distribution are negligible, the disformal coupling tends to stabilise the system.