Analyses are given of various processes involving matter fallinginto or coming out of black holes.
A significant amount of matter may fall into a black hole in agalactic nucleus or in a binary system. There gas with relatively highangular momentum is expected to form an accretion disk flowing into thehole. In this thesis the conservation laws of rest mass, energy, andangular momentum are used to calculate the radial structure of such adisk. The averaged torque in the disk and flux of radiation from thedisk are expressed as explicit, algebraic functions of radius.
Matter may be created and come out of the gravitational field ofa black hole in a quantum-mechanical process recently discovered byHawking. In this thesis the emission rates of massless particles byHawking's process are computed numerically. The resulting power spectraof neutrinos, photons, and gravitons emitted by a nonrotating hole aregiven. For rotating holes, the rates of emission of energy and angularmomentum are calculated for various values of the rotation parameter.The evolution of a rotating hole is followed as energy and angularmomentum are given up to the emitted particles. It is found that angularmomentum is lost considerably faster than energy, so that a blackhole spins down to a nearly nonrotating configuration before it loses alarge fraction of its mass. The implications are discussed for the lifetimes and possible present configurations of primordial blackholes (the only holes small enough for the emission to be significantwithin the present age of the universe.
As an astrophysical application, a calculation is given of thegamma-ray spectrum today from the emission by an assumed distributionof primordial black holes during the history of the universe. Comparisonwith the observed isotropic gamma-ray flux above about 100 MeV yieldsan upper limit of approximately 10^4 pc^(-3) for the average number densityof holes around 5 x 10^(14)g.(This is the initial mass of a nonrotatingblack hole that would just decay away in the age of the universe.) Theprospects are discussed for observing the final, explosive decay of anindividual primordial black hole. Such an observation could test thecombined predictions of general relativity and quantum mechanics andalso could provide information about inhomogeneities in the early universeand about the nature of strong interactions at high temperatures.
