The research to be carried out here is a renewal of a project of the same title. Building upon this previous work in which the precession and nonlinear saturation of the r-mode instability of neutron stars was examined, Dr. Wasserman and collaborators/students will undertake two major computational projects. The first is a numerical study of vortex lines and magnetic flux tubes in neutron star interiors. The work is motivated by the need to understand the precession of pulsar PSR B1828-11 and whether its slow period contradicts a conventional neutron superfluid/proton Type II superconductor core model. Critical to this is the strength of drag forces between superfluid vortices and superconducting flux tubes, which will be addressed here (if the mutual drag force between superfluid vortices and superconducting flux tubes is too strong, long period precession would not be possible). Second will be a study of how the nonlinear development and saturation of the r-mode instability affects the spin evolution of new and old accreting neutron stars. Recent work by Dr. Wasserman's group (supported by the NSF previous award) has shown that the r-mode instability tends to saturate at lower amplitudes than originally thought but the implications of this result on the subsequent spin evolution of neutron stars remains unexplored. Through this work, graduate students at Cornell will be trained in advanced and multidisciplinary (astrophysics, gravitational physics, condensed matter) theoretical research. Dr. Wasserman participates in the Harlow Shapley Lectureship program and will continue to lecture regularly on forefront topics in astrophysics (including this project) to diverse audiences, which include members of the public and high school students in addition to faculty and students at the host colleges.
