Dipartimento di Fisica

Geodesic motions are crucial in determining the fundamental features of spacetime. In this letter we provide evidence for a correspondence between the formation of black holes and the stability of circular null geodesics around the collapsing perturbation. We first show that the critical threshold for the collapse of cosmological perturbazione to form a black hole in radiation is well approximated by the threshold for the appearance of the first unstable circular orbit in a spherically symmetric background. We also show that the critical exponent in the scaling law of the primordial black hole mass close to the threshold is set by the instability of the orbits (Lyapunov coefficient) when a self-similar stage is developed close to criticality.

Authors: A.Ianniccari, A.Iovino, A.Kehagias, D.Perrone and A.Riotto

Magazine: Physical Review Letters