On the Vanishing of Love Numbers for Kerr Black Holes

TL;DR

This paper confirms that Kerr black holes have zero static Love numbers for gravitational, scalar, and electromagnetic fields, indicating a universal property of black holes in four-dimensional general relativity, with non-zero dissipative responses due to frame-dragging.

Contribution

It extends the vanishing of Love numbers to spin-0 and spin-1 perturbations and clarifies the distinction between conservative and dissipative responses using an invariant definition.

Findings

Static Love numbers vanish for Kerr black holes across spin-0, spin-1, and spin-2 fields.

Dissipative responses remain non-zero due to frame-dragging effects.

Vanishing Love numbers are a generic property in four-dimensional GR black holes.

Abstract

It was shown recently that the static tidal response coefficients, called Love numbers, vanish identically for Kerr black holes in four dimensions. In this work, we confirm this result and extend it to the case of spin-0 and spin-1 perturbations. We compute the static response of Kerr black holes to scalar, electromagnetic, and gravitational fields at all orders in black hole spin. We use the unambiguous and gauge-invariant definition of Love numbers and their spin-0 and spin-1 analogs as Wilson coefficients of the point particle effective field theory. This definition also allows one to clearly distinguish between conservative and dissipative response contributions. We demonstrate that the behavior of Kerr black holes responses to spin-0 and spin-1 fields is very similar to that of the spin-2 perturbations. In particular, static conservative responses vanish identically for spinning black holes. This implies that vanishing Love numbers are a generic property of black holes in four-dimensional general relativity. We also show that the dissipative part of the response does not vanish even for static perturbations due to frame-dragging.