On Black Hole Structures in Scalar-Tensor Theories of Gravity

TL;DR

This paper reviews black hole structures in scalar-tensor gravity theories, exploring properties of cold black holes and extending the analysis to k-essence models, highlighting horizon regularity constraints and scalar field behaviors.

Contribution

It provides a comprehensive review of black hole solutions in scalar-tensor theories, including new insights into horizon regularity and scalar field dynamics in k-essence models.

Findings

Cold black holes exhibit specific properties in scalar-gravity systems.

Horizon regularity imposes constraints leading to cold black hole or singular behaviors.

Extensions to k-essence theories reveal similar horizon and scalar field characteristics.

Abstract

We review some properties of black hole structures appearing in gravity with a massless scalar field, with both minimal and nonminimal coupling. The main properties of the resulting cold black holes are described. The study of black holes in scalar-gravity systems is extended to $k$-essence theories, and some examples are explicitly worked out. In these cases, even while the existence of horizons is possible, the metric regularity requirement on the horizon implies either a cold black type structure or a singular behavior of the scalar field.