Pulsars and the evolution of supernova remnants

If pulsars are responsible for the particle acceleration in the remnants and if the main energy loss is due to the expansion, then the radio flux of young supernova remnants is expected to be well below that obtained by extrapolating the flux-radius relation of older remnants to small radii. The periods of the pulsars would be comparable to those found in the Crab and Vela.