# Note on an elementary particle model with Bertotti-Robinson core

## TL;DR

This paper examines a classical model of an elementary particle or black hole with a Bertotti-Robinson core, demonstrating its stability against linear radial perturbations, which supports its viability as a non-singular solution.

## Contribution

It analyzes the stability of a spherically symmetric particle/black hole model with a Bertotti-Robinson core under linear radial perturbations, confirming its stability.

## Key findings

- Model is stable against linear radial perturbations.
- The stability holds with a linear equation of state.
- Supports the model as a non-singular particle/black hole solution.

## Abstract

Spherically symmetric classical model of an elementary particle or a black hole spacetime without central singularity had been constructed by O. B. Zaslavskii in PRD 70(2004)104017. In this model an extremal Reissner-Nordstr% \"{o}m (RN) black hole and a Bertotti-Robinson (BR) spacetime are glued at the horizon such that the inner/core spacetime is the regular BR while outside is the extremal RN. In this note we investigate the stability of such a particle / regular black hole against linear radial perturbations. The model turns out to be stable against such perturbations with a linear equation of state after the perturbation.