Primordial Black Holes and Hot Matter

Microscopic black holes explode with their temperature varying inversely as their mass. Such explosions would lead to the highest temperatures in the present universe, all the way to the Planck energy. The possibility that a quasi-stationary shell of hot matter surrounds these black holes has recently been proposed and studied with relativistic Boltzmann transport equations and with relativistic viscous fluid dynamics. For example, a black hole with a mass of 10$^{10}$ g has a Hawking temperature of 1 TeV, a Schwarszchild radius of 1.6$\times10^{-5}$ fm, a luminosity of 7$\times10^{27}$ erg/s, and has less than 8 minutes to live. It is an outstanding theoretical challenge to describe the conditions exterior to such microscopic black holes and a great challenge to finally detect them in the new millennium.