Speaker
Description
The metastability of the Higgs potential raises a long-standing fundamental question for early-universe cosmology: what is the nonlinear fate of rare inflationary fluctuations that cross a potential barrier into a negative-energy region? Using fully nonlinear spherically symmetric numerical relativity, we investigate the evolution of such fluctuations in a radiation-dominated universe. We find a robust two-stage collapse process. First, the negative-potential core forms a primordial black hole, hiding the unstable region behind an apparent horizon. The subsequent evolution is governed by the self-gravity of the surviving barrier region and exhibits two qualitatively distinct branches. In the subcritical regime the horizon grows and engulfs the entire configuration, whereas in the supercritical regime a transient wormhole geometry develops, accompanied by bifurcating trapping horizons and the formation of an inflating child-universe branch. Despite their dramatically different internal structures, both branches leave behind an ordinary primordial black hole as viewed from the parent universe. We also provide preliminary results in which this conclusion is qualitatively similar in the case where the black hole forms during inflation and persists into the radiation phase of evolution. These results provide a new perspective on the cosmological implications of metastable Higgs-like fields and the role of gravitational collapse in shielding unstable regions of field space.