Spin-Induced Scalarized Black Holes

It was recently shown that a scalar field suitably coupled to the Gauss- Bonnet invariant G can undergo a spin-induced linear tachyonic instability near a Kerr black hole. This instability appears only once the dimensionless spin j is sufficiently large, that is, j greater than or similar to 0.5. A tachyonic instability is the hallmark of spontaneous scalarization. Focusing, for illustrative purposes, on a class of theories that do exhibit this instability, we show that stationary, rotating black hole solutions do indeed have scalar hair once the spin-induced instability threshold is exceeded, while black holes that lie below the threshold are described by the Kerr solution. Our results provide strong support for spin-induced black hole scalarization.

Automated summary

A recently study shows that a scalar field coupled to the Gauss-Bonnet invariant can experience a spin-induced linear tachyonic instability near a Kerr black hole, only when the dimensionless spin j is greater than or equal to 0.5. Results demonstrate that black hole solutions do have scalar hair once the spin-induced instability threshold is exceeded, supporting the idea of spin-induced black hole scalarization.