On the motion of hairy black holes in Einstein-Maxwell-dilaton theories

TL;DR

This paper develops an effective point particle model for black holes in Einstein-Maxwell-dilaton theories, revealing how their scalar environment can cause significant deviations from general relativity in two-body dynamics.

Contribution

It introduces a phenomenological skeleton action for black holes in EMD theories, enabling analysis of many-body interactions and scalarization effects.

Findings

Black holes can undergo scalarization depending on their environment.

Scalarization leads to large deviations in two-body dynamics.

The first post-Keplerian Lagrangian for EMD theories is computed.

Abstract

Starting from the static, spherically symmetric black hole solutions in massless Einstein-Maxwell-dilaton (EMD) theories, we build a "skeleton" action, that is, we phenomenologically replace black holes by an appropriate effective point particle action, which is well suited to the formal treatment of the many-body problem in EMD theories. We find that, depending crucially on the value of their scalar cosmological environment, black holes can undergo steep "scalarization" transitions, inducing large deviations to the general relativistic two-body dynamics, as shown, for example, when computing the first post-Keplerian Lagrangian of EMD theories.