Black Hole Gravitational Waves in the Effective Field Theory of Gravity

TL;DR

This paper explores how gravitational waves propagate near black holes within an effective field theory of gravity, revealing effects on wave speed and quasinormal modes due to higher curvature operators.

Contribution

It provides a detailed analysis of gravitational wave behavior in effective field theory, including horizon properties and corrections to quasinormal frequencies.

Findings

Gravitational wave speed can be superluminal or subluminal depending on particle spin.

Gravitational waves are always luminal at the black hole horizon.

Higher curvature operators cause measurable corrections to quasinormal frequencies.

Abstract

We investigate the propagation of gravitational waves on a black hole background within the low energy effective field theory of gravity, where effects from heavy fields are captured by higher dimensional curvature operators. Depending on the spin of the particles integrated out, the speed of gravitational waves at low energy can be either superluminal or subluminal as compared to the causal structure observed by other species. Interestingly however, gravitational waves are always exactly luminal at the black hole horizon, implying that the horizon is identically defined for all species. We further compute the corrections on quasinormal frequencies caused by the higher dimensional curvature operators and highlight the corrections arising from the low energy effective field.