Charged black holes in string-inspired gravity: I. Causal structures and responses of the Brans-Dicke field

TL;DR

This paper explores the causal structures and field responses in charged black hole collapses within various string-inspired gravity models, revealing model-dependent horizons, no-hair properties, and novel phenomena like wormhole formation and inflation.

Contribution

It provides a comparative analysis of black hole collapse dynamics across multiple string-inspired gravity theories, highlighting differences in horizons, field behavior, and emergent phenomena.

Findings

Type IIA models have Cauchy horizons; others do not.

Asymptotic no-hair theorem holds in Type IIA models.

Ghost limit can induce inflation and create traversable wormholes.

Abstract

We investigate gravitational collapses of charged black holes in string-inspired gravity models, including dilaton gravity and braneworld model, as well as f(R) gravity and the ghost limit. If we turn on gauge coupling, the causal structures and the responses of the Brans-Dicke field depend on the coupling between the charged matter and the Brans-Dicke field. For Type IIA inspired models, a Cauchy horizon exists, while there is no Cauchy horizon for Type I or Heterotic inspired models. For Type IIA inspired models, the no-hair theorem is satisfied asymptotically, while it is biased to the weak coupling limit for Type I or Heterotic inspired models. Apart from string theory, we find that in the ghost limit, a gravitational collapse can induce inflation by itself and create one-way traversable wormholes without the need of other special initial conditions.