Formation of frozen stars from collapsing matter by tunneling
Phys. Rev. D 113, 104008 – Published 6 May, 2026
DOI: https://doi.org/10.1103/hxll-2lr3
Abstract
The frozen star is a type of black hole mimicker; an ultracompact object whose exterior geometry resembles that of a general relativistic black hole but differs in its matter composition and in the regularity of its interior geometry. It is sourced by a spherically symmetric collection of open-string flux tubes, which posses an extremely anisotropic energy-momentum-stress tensor with maximally negative radial pressure. The frozen star represents an effective classical description of the highly quantum, closed-string polymer model. A key challenge for any model of a black hole mimicker is to explain how such objects can form from a collapsing body of matter. We started to address this important problem in [1] by adapting the Euclidean-action method of Gibbons and Hawking to show that the transition into a frozen star is likely. Here, we improve on our previous results by showing that the transition probability for a collapsing shell of matter to tunnel quantum mechanically into a frozen star is unity, up to negligible corrections. Our conclusion is that such a transition is therefore inevitable.
