On critical collapse of gravitational waves

Understand

An axisymmetric collapse of non-rotating gravitational waves is numerically investigated in the subcritical regime where no black holes form but where curvature attains a maximum and decreases, following the dispersion of the initial wave packet.

• We focus on a curvature invariant with dimensions of length, and find that near the threshold for black hole formation it reaches a maximum along concentric rings of finite radius around the axis.
• In this regime the maximal value of the invariant exhibits a power-law scaling with the approximate exponent 0.38, as a function of a parametric distance from the threshold.
• In addition, the variation of the curvature in the critical limit is accompanied by increasing amount of echos, with nearly equal temporal and spatial periods.