Two main projects will be studied that are important for understanding the long term behavior of the rotation of neutron stars. One project will focus on the precession of neutron stars, with a particular emphasis on the best observed candidate for a precessing pulsar, PSR 1828-11, and focusing on what can be learned about the interior properties of neutron stars, for example coupling between the fluid interior and crustal structures. The idea that a rotating star with a magnetic field tilted with respect to the rotation access must precess (an idea proposed long ago) will be applied to pulsars. For neutron stars, the PI has proposed that observable precession is a natural consequence of one form of superconductivity, or large internal toroidal fields, or both, which would imply much larger core magnetic stresses than would follow from the dipole field strength strengths that are inferred from the rate of pulsar spindown. Implications for pulsar observations and gravitational radiation detection will be explored. The other project will focus on the nonlinear development of the r-mode fluid oscillation instability of fast rotating neutron stars using a formalism that includes interactions among inertial modes of the star. Particular emphasis will be placed on simulating the nonlinear dynamics of many interacting inertial modes (wobbles). Although the results will pertain specifically to neutron stars, the techniques ought to be applicable to a broad range of problems in which numerous normal modes can interact resonantly to truncate an instability.
Broader impacts. This research will include: the training of a pair of Cornell Ph. D. students, one of whom is an outstanding young woman; the anticipated inclusion of an undergraduate in assessing the observational implications of some of the work; public lectures to be given by the PI under the auspices of the Harlow Shapley program of the American Astronomical Society; multidisciplinary collaboration with colleagues in pulsar astronomy and gravitation physics both at Cornell and elsewhere; broad dissemination of the results, where feasible, at conferences and workshops in related fields (condensed matter physics, gravitational physics, nonlinear dynamics).
