“Kerrr” black hole: The lord of the string

Kerrr in the title is not a typo. The third "r" stands for "regular", in the sense of pathology-free, rotating black hole. We exhibit a long search-for, exact, Kerr-like, solution of the Einstein equations with novel features: i) no curvature ring singularity; ii) no "anti-gravity" universe with causality violating timelike closed world-lines; iii) no "super-luminal" matter disk. The ring singularity is replaced by a classical, circular, rotating string with Planck tension representing the inner engine driving the rotation of all the surrounding matter. The resulting geometry is regular and smoothly interpolates among inner Minkowski space, borderline deSitter and outer Kerr universe. The key ingredient to cure all unphysical features of the ordinary Kerr black hole is the choice of a "noncommutative geometry inspired" matter source as the input for the Einstein equations, in analogy with spherically symmetric black holes described in earlier works.