Abundance and evolution of radio-loud quasars in cold dark matter cosmology

The power of the jets and radio activity of quasars appears to be determine d by the spin parameter of the black holes in the host galaxies. In this pa per, the space number density of radio-loud quasars in cold dark matter cos mologies with biasing factors b(f) = 1 and b(f) = 1.5 is computed, assuming that radio-loud quasars are created when two galaxies merge, forming a rap idly spinning black hole in the center. Our results are consistent with the observational data if quasars have lifetimes of similar to 10(7)-10(8) yr. Our present model supports the idea that some of the luminous radio galaxi es may not contain a quasar in their centers.