Zooming into the horizon region of black hole-type objects

TL;DR

This paper investigates how higher-order curvature terms in quantum gravity can drastically alter black hole solutions, potentially removing horizons and creating naked singularities or wormholes, with implications for observational constraints.

Contribution

It provides the first systematic analysis of the impact of quadratic and cubic curvature terms on black hole horizons within modified gravity theories.

Findings

Higher-derivative terms induce extra degrees of freedom.

These terms can eliminate the event horizon, leading to naked singularities or wormholes.

The effects depend on the coupling constants in the asymptotic region.

Abstract

A universal prediction of quantum gravity is that the dynamics of general relativity is augmented by interactions that are of higher order in the spacetime curvature. Numerical explorations indicate that such terms may have a drastic impact on black hole-type solutions by modifying the geometry close to the would-be event horizon in a substantial way. In this work, we perform the first systematic investigation of this blow-up mechanism within general relativity supplemented by quadratic gravity terms, the Goroff-Sagnotti counterterm, the combination of the two, and Einstein-Cubic Gravity. By studying linear perturbations of the Schwarzschild solution close to the Schwarzschild radius, we discover the following picture: the higher-derivative terms giving rise to extra degrees of freedom play a distinguished role. Once couplings associated with these terms enter the solution in the asymptotically flat region, a blow-up mechanism removes the event horizon and one deals with either a naked singularity or a wormhole. We believe that this finding is highly relevant when constraining the coefficients appearing in the Wilsonian description of gravity by observations.