2001ApJ...557L..61A

Neutron stars may be surrounded by fallback disks formed from supernova core collapse. If the disk circumscribes the light cylinder, the neutron star will be an active radio pulsar spinning down under the propeller spin-down torque applied by the disk as well as the usual magnetic dipole radiation torque. Evolution across the P-P{dot} diagram is very rapid when pulsar spin-down is dominated by the propeller torque. This explains the distribution of pulsars in the P-P{dot} diagram.