Problem in pulsar evolution

Two models of evolution for pulsars are investigated. It is found that a model assuming the same initial magnetic moment but different time scales for its decay for different pulsars fails to reproduce the densities of pulsars in the logP vs logP diagram. A model assuming different initial magnetic moments but the same decay time for all pulsars can reproduce the observed densities for high-P pulsars with the exception of a region of apparently anomalous low density (a ''gap'' in P). Assuming that the gap is a statistical fluctuation, the model is used to derive the pulsar birthrate in the galaxy. The birthrate is found to be highly dependent on the pulsar beaming model assumed, but is greater than 1 pulsar/8 yr in the most conservative case and less than 1 pulsar/8 yr in the least conservative case