Classical model of elementary particle with Bertotti-Robinson core and extremal black holes

TL;DR

This paper explores classical models of elementary particles by examining the possibility of smoothly gluing extremal Reissner-Nordström and Kerr-Newman black hole solutions to other metrics, focusing on removing singularities and the implications of such constructions.

Contribution

It introduces a new approach to modeling elementary particles by gluing extremal black hole solutions to the Bertotti-Robinson metric, addressing singularity removal and stress behavior.

Findings

Extremal RN cannot be smoothly glued to Minkowski space due to infinite stresses.

Gluing extremal RN to Bertotti-Robinson metric results in vanishing stresses at the horizon.

The model extends to extremal Kerr-Newman black holes with rotating Bertotti-Robinson analogs.

Abstract

We discuss the question, whether the Reissner-Nordstr\"{o}m RN) metric can be glued to another solutions of Einstein-Maxwell equations in such a way that (i) the singularity at r=0 typical of the RN metric is removed (ii), matching is smooth. Such a construction could be viewed as a classical model of an elementary particle balanced by its own forces without support by an external agent. One choice is the Minkowski interior that goes back to the old Vilenkin and Fomin's idea who claimed that in this case the bare delta-like stresses at the horizon vanish if the RN metric is extremal. However, the relevant entity here is the integral of these stresses over the proper distance which is infinite in the extremal case. As a result of the competition of these two factors, the Lanczos tensor does not vanish and the extremal RN cannot be glued to the Minkowski metric smoothly, so the elementary-particle model as a ball empty inside fails. We examine the alternative possibility for the extremal RN metric - gluing to the Bertotti-Robinson (BR) metric. For a surface placed outside the horizon there always exist bare stresses but their amplitude goes to zero as the radius of the shell approaches that of the horizon. This limit realizes the Wheeler idea of "mass without mass" and "charge without charge". We generalize the model to the extremal Kerr-Newman metric glued to the rotating analog of the BR metric.