Dynamics of near-Nariai black holes and the ‘shark fin’ parameter region

Ascertain whether a near-Nariai Reissner–Nordström–de Sitter black hole can dynamically exit the allowed mass–charge parameter space (the ‘shark fin’ region), clarifying its evolution under charge and mass changes in the presence of a cosmological horizon.

Background

In discussing charged black holes in de Sitter space, the authors note that Schwinger production may form a particle cloud whose extent is set by the Compton wavelength and may significantly affect the effective mass and charge near the Nariai regime.

They explicitly connect this intuition to the unresolved issue of whether near-Nariai black holes can dynamically leave the allowed parameter region—the so-called ‘shark fin’ region—and suggest that accounting for the particle cloud may smooth the evolution, but leave the central question open.