Universality in axisymmetric vacuum collapse

Evidence of universality is observed in the critical behavior of axisymmetric vacuum gravitational collapse. The threshold of black hole formation in the future development of time-antisymmetric initial data is found numerically and compared to previous results based on ingoing pulses of gravitational waves. The power-law behavior of the black hole mass is again found near the critical point and the critical exponent value β0.36 is consistent with our previous determination despite stark differences in the two sets of initial data. Similar evidence of universality is exhibited by the scaling factor Δ of the echoes in the gravitational field produced in the central region of collapse.