Critical phenomena and self-similarity in the gravitational collapse of radiation fluid

We observe critical phenomena in spherical collapse of radiation fluid. A sequence of spacetimes S[η] is numerically computed, containing models (η≪1) that adiabatically disperse and models (η≫1) that form a black hole. Near the critical point (${\mathrm{\eta }}_{\mathit{c}}$), evolutions develop a self-similar region within which collapse is balanced by a strong, inward-moving rarefaction wave that holds m(r)/r constant as a function of a self-similar coordinate ξ. The self-similar solution is known and we show near-critical evolutions asymptotically approaching it. A critical exponent β≃0.36 is found for supercritical (η>${\mathrm{\eta }}_{\mathit{c}}$) models.