Gravitational footprints of black holes and their microstate geometries

We construct a family of non-supersymmetric extremal black holes and their horizonless microstate geometries in four dimensions. The black holes can have finite angular momentum and an arbitrary charge-to-mass ratio, unlike their supersymmetric cousins. These features make them and their microstate geometries astrophysically relevant. Thus, they provide interesting prototypes to study deviations from Kerr solutions caused by new horizon-scale physics. In this paper, we compute the gravitational multipole structure of these solutions and compare them to Kerr black holes. The multipoles of the black hole differ significantly from Kerr as they depend non-trivially on the charge-to-mass ratio. The horizonless microstate geometries (that are comparable in size to a black hole) have a similar multipole structure as their corresponding black hole, with deviations to the black hole multipole values set by the scale of their microstructure.

Automated summary

We constructed a family of non-supersymmetric extremal black holes and their horizonless microstate geometries, which are astrophysically relevant and provide interesting prototypes for deviations from Kerr solutions. The gravitational multipole structure of these solutions differ significantly from Kerr, depending non-trivially on the charge-to-mass ratio. The horizonless microstate geometries have a similar multipole structure as their corresponding black hole, with deviations set by the scale of their microstructure.