Black hole singularities: a new critical phenomenon

TL;DR

This paper numerically investigates how the nature of singularities inside charged black holes changes with different scalar field profiles, revealing a critical phenomenon that affects the black hole's internal structure.

Contribution

It identifies a new critical exponent that determines whether the singularity inside a charged black hole is mixed or fully spacelike, advancing understanding of black hole internal dynamics.

Findings

Existence of a critical exponent $oldsymbol{eta_{crit}}$ separating different singularity structures.

For $oldsymbol{eta < eta_{crit}}$, singularity is mixed (spacelike and null).

For $oldsymbol{eta > eta_{crit}}$, singularity is fully spacelike and blocks the tunnel.

Abstract

The singularitiy inside a spherical charged black hole, coupled to a spherical, massless scalar field is studied numerically. The profile of the characteristic scalar field was taken to be a power of advanced time with an exponent $\alpha>0$. A critical exponent $\alpha_{\rm crit}$ exists. For exponents below the critical one ($\alpha<\alpha_{\rm crit}$) the singularity is a union of spacelike and null sectors, as is also the case for data with compact support. For exponents greater than the critical one ($\alpha>\alpha_{\rm crit}$) an all-encompassing, spacelike singularity evolves, which completely blocks the ``tunnel'' inside the black hole, preventing the use of the black hole as a portal for hyperspace travel.