Critical phenomena in the gravitational collapse of electromagnetic waves

Baumgarte, Thomas W., Gundlach, Carsten and Hilditch, David (2019) Critical phenomena in the gravitational collapse of electromagnetic waves. Physical Review Letters, 123 (17), [171103]. (doi:10.1103/PhysRevLett.123.171103).

Record type: Article

Abstract

We numerically investigate the threshold of black-hole formation in the gravitational collapse of electromagnetic waves in axisymmetry. We find approximate power-law scaling
ρ
max
∼
(
η
∗
−
η
)
−
2
γ
of the maximum density in the time evolution of near-subcritical data with
γ
≃
0.145
, where
η
is the amplitude of the initial data. We directly observe approximate discrete self-similarity in near-critical time evolutions with a log-scale echoing period of
Δ
≃
0.55
. The critical solution is approximately the same for two families of initial data, providing some evidence of universality. Neither the discrete self-similarity nor the universality, however, are exact. We speculate that the absence of an exactly discrete self-similarity might be caused by the interplay of electromagnetic and gravitational wave degrees of freedom, or by the presence of higher-order angular multipoles, or both, and discuss implications of our findings for the critical collapse of vacuum gravitational waves.