Glitches, torque evolution and the dynamics of young pulsars

The Crab pulsar has suffered in 1975 and 1989 two glitches in which thefrequency did not relaxed to the extrapolated pre-glitch value but rather spunup showing long-term changes in the frequency derivative dot Omega. Thisparticular behaviour has been interpreted as evidence for an evolution of thetorque acting upon the star. A variable torque may be related to non-canonicalbraking indexes, for which some determinations have been possible. We brieflyanalyse in this work the consistency of postulating a growth in the anglebetween the magnetic moment and the rotation axis as the cause of such events.We show that this hypothesis leads to the determination of the initial period,initial and present angles, according to the assumed angle growth, for youngpulsars whose respective braking indices n_{obs} and jerk parameters m_{obs}are known, and some insights on the equation of state.Comment: 23 pages, PlainTex, to appear in MNRA