ON THE COOLING OF NEUTRON-STARS

It has recently been pointed out that many models of dense nuclear mat ter allow the direct URCA process in highly dense systems like neutron stars. In view of this, we have calculated the energy loss in dense n uclear matter as a result of such processes at finite temperatures. Fo r the description of nuclear matter we have used Walecka's mean-field theory. For the neutrino emissivity rates we have employed the Iwamoto model and evaluated the angular integrals involved exactly. We find t hat the emissivity rate is density dependent, being almost a constant at high densitites, while at low densities it shows an exponential beh aviour with temperature rather than the usual power law.