Spontaneous vectorization of electrically charged black holes

TL;DR

This paper extends the concept of spontaneous scalarization to vector fields in Einstein-Maxwell-Vector models, revealing new undercharged, entropically favored black hole solutions with a non-minimally coupled vector field.

Contribution

It introduces a higher spin generalization of spontaneous scalarization, demonstrating the existence of vectorized black holes that bypass no-hair theorems in Einstein-Maxwell-Scalar models.

Findings

Vectorized black holes are always undercharged.

These solutions are entropically preferred over Reissner-Nordström black holes.

The domain of existence and solution profiles are characterized.

Abstract

In this work, we generalise the spontaneous scalarization phenomena in Einstein-Maxwell-Scalar models to a higher spin field. The result is an Einstein-Maxwell-Vector model wherein a vector field is non-minimally coupled to the Maxwell invariant by an exponential coupling function. We show that the latter guarantees the circumvention of an associated no-hair theorem when the vector field has the form of an electric field. Different than its scalar counterpart, the new spontaneously vectorized Reissner-Nordstr\"om (RN) black holes are, always, undercharged while being entropically preferable. The solution profile and domain of existence are presented and analysed.