Primary black-hole scalar charges and kinetic screening in $K$-essence-Gauss-Bonnet gravity

TL;DR

This paper investigates how scalar charges of black holes are influenced by kinetic terms in K-essence-Gauss-Bonnet gravity, revealing conditions under which scalar charges become primary and analyzing stability and screening effects.

Contribution

It introduces the impact of nontrivial kinetic terms on black hole scalar charges and explores the transition from secondary to primary charges in cosmological settings.

Findings

Kinetic screening affects scalar charge magnitude.

Time-dependent scalar fields enable primary scalar charges.

Stability analysis of scalar and gravitational modes.

Abstract

Black holes beyond General Relativity may carry non-standard charges that impact their phenomenology. We study how the scalar charge that is induced by the scalar-Gauss-Bonnet coupling is affected by the presence of a nontrivial kinetic term $K(X)$. We discuss the corresponding kinetic screening in the asymptotically flat, static solution first. We then turn to the case where self-accelerating cosmology is driven by $K(X)$, finding that the time-dependence of the scalar field opens up the parameter space, turning the black-hole scalar charge from secondary to primary. We provide a stability analysis and a measure of the intensity of the kinetic screening from the quartic dispersion relation of the mixed scalar and gravitational modes.