Spin evolution of pulsars with weakly coupled superfluid interiors

We discuss the spin evolution of pulsars in the case where a superfluid com ponent of the star is coupled to the observable crust on long, spin-down ti mescales. The momentum transfer from the superfluid interior results in an apparent decay of the external torque and, after a dramatic increase, in an asymptotic decrease of the generic value of the braking index, e.g., n = 3 , to values n similar to 2.5 if the magnetic held of the star does not deca y over its lifetime. In the case where an exponential decay of the magnetic field toward a residual value occurs, the star undergoes a spin-up phase a fter which it could emerge in the millisecond sector of the P-(P) over dot diagram.