Critical scalarization and descalarization of black holes in a generalized scalar-tensor theory

TL;DR

This paper investigates the nonlinear dynamics of black hole scalarization and descalarization within a generalized scalar-tensor theory, revealing new critical phenomena and effects of scalar couplings on stability and evolution.

Contribution

It introduces a new type I critical phenomenon in black hole phase transitions and analyzes how scalar-Ricci coupling influences hyperbolicity and stability in nonlinear evolution.

Findings

Identification of a typical type I critical phenomenon in scalarization.

Existence of a marginally stable attractor at the descalarization threshold.

Scalar-Ricci coupling can suppress elliptic regions and enhance computational stability.

Abstract

We study the critical dynamics in the scalarization and descalarization in the fully nonlinear dynamical evolution in a general theory with scalar field coupling with both Gauss-Bonnet invariant and Ricci scalar. We explore how the Gauss-Bonnet term triggers the black hole scalarization. A typical type I critical phenomenon is observed, where an unstable critical solution emerges at the threshold and acts as an attractor in the dynamical scalarization. In the descalarization, a marginally stable attractor exists at the threshold of the first order phase transition in shedding off black hole hair. This is a new type I critical phenomenon in the black hole phase transition. Implications of these findings are discussed from the perspective of thermodynamic properties and perturbations for static solutions. We examine the effect of scalar-Ricci coupling on the hyperbolicity in the fully nonlinear evolution and find that such coupling can suppress the elliptic region and enlarge parameter space in computations.