Theoretical Astrophysics, Eberhard Karls University of Tübingen, Tübingen 72076, Germany.
INRNE-Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria.
Phys Rev Lett. 2018 Mar 30;120(13):131103. doi: 10.1103/PhysRevLett.120.131103.
In the present Letter, we consider a class of extended scalar-tensor-Gauss-Bonnet (ESTGB) theories for which the scalar degree of freedom is excited only in the extreme curvature regime. We show that in the mentioned class of ESTGB theories there exist new black-hole solutions that are formed by spontaneous scalarization of the Schwarzschild black holes in the extreme curvature regime. In this regime, below certain mass, the Schwarzschild solution becomes unstable and a new branch of solutions with a nontrivial scalar field bifurcates from the Schwarzschild one. As a matter of fact, more than one branch with a nontrivial scalar field can bifurcate at different masses, but only the first one is supposed to be stable. This effect is quite similar to the spontaneous scalarization of neutron stars. In contrast to the standard spontaneous scalarization of neutron stars, which is induced by the presence of matter, in our case, the scalarization is induced by the curvature of the spacetime.
在这封信件中，我们考虑了一类扩展的标量-张量-高斯-博内（ESTGB）理论，其中标量自由度仅在极端曲率状态下被激发。我们表明，在所考虑的 ESTGB 理论类中，存在新的黑洞解，这些解是由极端曲率状态下的 Schwarzschild 黑洞的自发标量化形成的。在该状态下，在低于某个质量时，Schwarzschild 解变得不稳定，并且具有非平凡标量场的新解分支从 Schwarzschild 解分支分叉出来。实际上，在不同的质量下可能会有多个具有非平凡标量场的分支分叉出来，但只有第一个分支被认为是稳定的。这种效应与中子星的自发标量化非常相似。与由物质引起的标准的中子星的自发标量化不同，在我们的情况下，标量化是由时空曲率引起的。
