Screening of dipolar emission in two-scale Gauss-Bonnet gravity

TL;DR

This paper investigates black holes in a modified gravity theory combining Gauss-Bonnet and Galileon interactions, revealing how the hierarchy of energy scales influences black hole properties and allows for observational tests in the strong-field regime.

Contribution

It introduces a multi-scale effective field theory of scalar Gauss-Bonnet gravity with a cubic Galileon term, demonstrating screening effects and phenomenological implications for black holes.

Findings

Smaller black holes are possible due to the cubic interaction.

Screening mechanism near the horizon allows large couplings to be consistent with bounds.

Observable quantities are significantly affected for small black holes.

Abstract

We study black holes in shift-symmetric scalar Gauss-Bonnet gravity extended by a cubic Galileon interaction with a distinct energy scale. Introducing this hierarchy profoundly modifies the theory's phenomenology. The cubic interaction allows for smaller black holes, and can generate a screening mechanism near the horizon, making large Gauss-Bonnet couplings consistent with gravitational-wave bounds. Observable quantities such as the scalar charge, the innermost stable circular orbit, and its frequency are most affected for small black holes. The resulting multi-scale effective field theory remains technically natural and offers new avenues to probe gravity in the strong-field regime.