Simulations of gravitational collapse in null coordinates: II. Critical collapse of an axisymmetric scalar field

Understand

We present the first numerical simulations in null coordinates of the collapse of nonspherical regular initial data to a black hole.

• We restrict to twist-free axisymmetry, and re-investigate the critical collapse of a non-spherical massless scalar field.
• We find that the Choptuik solution governing scalar field critical collapse in spherical symmetry persists when fine-tuning moderately non-spherical initial data to the threshold of black hole formation.
• The non-sphericity evolves as an almost-linear perturbation until the end of the self-similar phase, and becomes dominant only in the final collapse to a black hole.