Symmetry-breaking rotational instabilities may operate in the gravitational collapse of a rapidly rotating stellar core. During the collapse, the external spacetime undergoes dynamical changes in response to the changing shape of the collapsing object and gravitational radiation is emitted. The growth of nonaxisymmetric modes from the dynamical bar mode instability, and the related secular instability, may be important factors in shaping the structure of the collapse and supernovae explosion.

If a significant amount of angular momentum remains in an initially axisymmetric core, collapse may be slowed or temporarily stalled by centrifugal forces associated with rotation. In such a scenario, global rotational instabilities may become important and can potentially produce detectable amounts of gravitational radiation. These instabilities allow growth of non-axisymmetric structures on the dynamical time scale, which is the same time scale on which core collapse occurs. The growth of these modes provide a means for transport of angular momentum out of the core into the surrounding envelope. The breaking of axisymmetry enables loss of angular momentum from the core through the emission of gravitational radiation allowing collapse to continue to a supernovae. Thus, instabilities may play an important role in the formation and subsequent evolution of the neutron star. Asymmetry of the collapsed core coupled with high rotational speeds may give rise to the large proper motions observed in some pulsars.

I have explored the effects fluid compressibility, and rotation rate on the onset and subsequent behavior of the dynamical bar instability. Currently I am investigating the effects of General Relativity on dynamically and secularly unstable pre-supernova stellar cores.