Universality in the collapse of rotating gravitational waves

Choptuik's discovery of critical phenomena in the collapse of a spherically symmetric massless scalar field has spurred much interest over the years to explore critical collapse in more general settings. By evolving one-parameter families of initial data, it was found that spacetimes near the threshold of collapse or dispersion exhibited type II critical phenomena, with the properties of universality, scaling, and self-similarity. Shortly afterwards, similar results were obtained by Abrahams and Evans (and more recently by Sorkin) for the critical collapse of axisymmetric non-rotating gravitational waves. Despite many investigations into the critical collapse of other spherically symmetric or axisymmetric configurations, there has been relatively little headway on studying the critical collapse of non-axisymmetric configurations, which may carry angular momentum. In this talk, I will report on progress in simulating the critical collapse of non-axisymmetric rotating gravitational waves, which instead exhibit signs of type I critical phenomena, and comment on evidence for universality.