Kasner geometries inside holographic superconductors

TL;DR

This paper investigates how modifications to holographic superconductor models, including axion fields and EMS coupling, affect black hole interior dynamics and Kasner geometries, revealing new behaviors like delayed collapse and altered oscillations.

Contribution

Introduces axion and EMS coupling modifications to holographic superconductor models, analyzing their impact on interior black hole geometries and Kasner regimes.

Findings

Increased EMS coupling delays collapse near the horizon.

Oscillations disappear with stronger EMS coupling.

Kasner regimes emerge after large-r collapse instead of near the horizon.

Abstract

The recent study of holographic superconductors has shown the emergence of a Kasner universe behind the event horizon. This paper serves to add to the discussion by introducing two modifications to the holographic superconductor model: an axion field term and an Einstein-Maxwell-scalar (EMS) coupling term. We first discuss the effect the modification parameters have on the condensate then explore the black hole interior dynamics. Features previously identified in the interior are found in the model presented, including the collapse of the Einstein-Rosen bridge, Josephson oscillations and Kasner inversions/transitions. However, we find that by increasing the EMS coupling parameter, the collapse does not occur near the axion-Reissner-Nordstr\"om horizon and the oscillations are no longer present; the geometry entering into a Kasner regime after a large-$r$ collapse instead.