Spontaneous vectorization of electrically charged black holes

In this work, we generalize 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 nonminimally 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 analyzed.