Very high frequency gravitational wave background in the universe

Abstract

Astrophysical sources of high frequency gravitational radiation are considered in association with a new interest in the very sensitive HFGW receivers required for the laboratory GW Hertz experiment. Special attention is paid to the phenomenon of primordial black-hole evaporation. It acts as a black body to all kinds of radiation, including gravitons, and, therefore, emits an equilibrium spectrum of gravitons during its evaporation. A limit on the density of high frequency gravitons in the universe is obtained, and the possibility of detecting them is briefly discussed.