XII BLACK HOLES WORKSHOP

Guimarães 19-20^th December 2019

We investigate static and spherically symmetric black hole (BH) solutions in the shift-symmetric degenerate higher-order scalar-tensor (DHOST) theories with and without the assumption that the kinetic term of the scalar field is constant. In the case of a constant kinetic term, we obtain Schwarzschild and Schwarzschild de Sitter BH solutions with nontrivial profile of the scalar field. We will also check the compatibility of the obtained solutions with degeneracy conditions, and show that BHs in cubic-order DHOST theories are strongly disfavored and quadratic theories are the most viable classes. In the case of a nonconstant kinetic term, we obtain BH solutions which possess neither Schwarzschild nor Schwarzschild de Sitter metrics. First, we provide our scheme to find analytic static and spherically symmetric vacuum solutions by reducing the higher-order equations to the second order ones with degeneracy conditions. We then consider explicit models to apply our scheme to find the exact BH solutions. These solutions can be asymptotically flat only for the tuned case. We also show that the BH solutions obtained in our analysis are mode stable against the odd-parity perturbations.

Oral presentation: yes. Poster: no.