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 (ηc), 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}>ηc) models.