Physics Colloquium: Theoretical Constraints on Neutron Star Superfluidity from Pulsar Precession

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Abstract: 

Neutron stars are cosmic laboratories for matter at extreme densities. Although their rotation is typically extraordinarily stable, many pulsars exhibit sudden spin-ups known as glitches, and some may also show slow wobbling motions, or precession. Glitches are widely believed to be triggered by the pinning and unpinning of superfluid vortices to nuclei in the solid crust.  In this talk, I will show that interactions between quantum vortices and the crystalline lattice in the crust also play a key role in the star’s precession dynamics. In particular, the 35-day modulation observed in Her X-1—an accreting neutron star—if interpreted as nearly free precession, as suggested by recent polarization measurements, implies that vortices must remain unpinned for at least hundreds of years and experience extremely low drag as they move through the lattice. This stands in sharp tension with conventional expectations.

Event Organizer: Prof. Michael Geller