Masato Minamitsuji, in a work published by Physical Review D, discovers new black hole solutions. The paper, now published , analyses what happens in the black hole spacetime when the cosmological constant is added to a scalar-tensor theory with nonminimal derivative coupling to the Einstein tensor. It concludes that the black hole spacetime will always approach anti-de Sitter (AdS) space at the asymptotic infinity.
The scalar-tensor gravitational theory with nonminimal derivative coupling to the Einstein tensor is an important building block of the most general scalar-tensor gravitational theories, which have become increasingly important to explain today's accelerated expansion of the universe. Minamitsuji’s article proves that, independently of the value of the cosmological constant, the black hole spacetime will always approach AdS at the asymptotic infinity, because the effect of the nonminimal coupling always dominates the system. Minamitsuji’s article concludes that the solution in four dimensions may not be suitable for an application to astrophysical or cosmological problems. But the type of nonminimal coupling considered in his article also appears as the leading order corrections to string theory. Therefore, a careful study of this model may give more insight on more fundamental theories.