Cloud Screening of extremal charged BTZ black hole

TL;DR

This paper investigates how a charged scalar field interacts with an extremal charged BTZ black hole's near-horizon region, revealing an instability that leads to a scalar cloud formation and electric flux screening, thus modeling electric screening phenomena.

Contribution

It provides an analytical study of scalar cloud formation and electric screening in extremal charged BTZ black holes, connecting near-horizon instability to self-consistent stationary solutions.

Findings

Scalar field instability triggered by BF bound violation.

Formation of a scalar cloud supported by Schwinger pair production.

Partial screening of electric flux in the black hole background.

Abstract

We study the dynamics of a charged scalar field in the near-horizon region of an extremal charged BTZ black hole. The near-horizon geometry contains an AdS2 throat with a constant electric field, which lowers the effective mass of the scalar and can trigger a violation of the AdS2 Breitenlohner-Freedman bound. We show that this instability is resolved by the formation of a static scalar cloud supported by Schwinger pair production. The condensate backreacts on the gauge field and partially screens the electric flux, leading to a self-consistent stationary configuration. The scalar profile is obtained analytically from the near-horizon equations and exhibits the characteristic behavior of a BF-violating mode in AdS2. We analyze the associated boundary conditions, the induced charge density, and the resulting modification of the electric field. The resulting configuration can be interpreted as an electric analogue of known magnetic hairy black hole solutions. Our results provide a concrete realization of electric screening in extremal charged black holes and clarify the role of near-horizon dynamics in shaping the infrared structure of the solution.