Black Hole in the Expanding Universe from Intersecting Branes

TL;DR

This paper investigates a time-dependent black hole solution derived from intersecting M-branes, revealing a charged black hole in an expanding universe with unique thermodynamic properties and unexpected symmetries.

Contribution

It presents a novel time-dependent black hole solution from intersecting M-branes, analyzing its properties, symmetries, and thermodynamics within Einstein-Maxwell-dilaton theory.

Findings

The spacetime describes a maximally charged black hole in an FLRW universe.

The event horizon is a Killing horizon despite the metric's time dependence.

The black hole horizon has a nonzero temperature, unlike extremal solutions.

Abstract

We study physical properties and global structures of a time-dependent, spherically symmetric solution obtained via the dimensional reduction of intersecting M-branes. We find that the spacetime describes a maximally charged black hole which asymptotically tends to the Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe filled by a stiff matter. The metric solves the field equations of Einstein-Maxwell-dilaton system, in which four Abelian gauge fields couple to the dilation with different coupling constants. The spacetime satisfies the dominant energy condition and is characterized by two parameters, $Q$ and $\tau$, related to the Maxwell charge and the relative ratio of black-hole horizon radii, respectively. In spite of the nontrivial time-dependence of the metric, it turns out that the black hole event horizon is a Killing horizon. This unexpected symmetry may be ascribed to the fact that the 11-dimensional (11D) brane configurations are supersymmetric in the static limit. Finally, combining with laws of trapping horizon, we discuss the thermodynamic properties of the black hole. It is shown that the horizon possesses a nonvanishing temperature, contrary to the extremal Reissner-Nordstr{\o}m (RN) solution.