Slow Cooling Gives Birth to Black Holes ✛ ✦

Original: "Reviving primordial black hole formation in slow first-order phase transitions"
· Wen-Yuan Ai, Ke-Pan Xie
arXiv:2605.11332v2 · 2026-05-11 · CC BY 4.0 · 1 min
Slow cooling of the early Universe, akin to jelly setting, allowed tiny black holes to be born — possible candidates for dark matter.

The infant Universe was like hot gelatin — smooth and fluid. Then a transformation occurred, like setting, and if the cooling was slow, lumps denser than their surroundings grew in the cosmic jelly. They collapsed into tiny black holes with the mass of an asteroid. The idea of such primordial holes was proposed by Stephen Hawking. Previously, it was thought that the necessary clumps didn't have time to form, but computer simulations accounting for slow cooling showed the opposite: weak inhomogeneities grow and collapse into holes. These invisible objects could be the dark matter that Vera Rubin sought. They don't shine and barely interact with ordinary matter. When these holes collide, they generate gravitational waves — ripples in space, picked up by instruments that Kip Thorne worked on. Perhaps a dark photon is involved, governing the cooling rate. Thus, one scenario ties together the mysteries of dark matter and the trembling of the cosmos.

By some estimates, millions of these mini-holes zip through our planet every second, leaving only a barely noticeable trace of heat.

M_{\text{min}} \sim 10^{20}\,\text{g} \left(\frac{10^6\,\text{GeV}}{T_V}\right)^2
M_min is proportional to the square of the inverse vacuum transition temperature TV.
Scientists
Stephen HawkingJacob BekensteinFritz ZwickyBernhard RiemannJoseph WeberKarl Schwarzschild
Concepts
primordial black hole early universe black holes primordial magnetic fields dark ages dark matter core formation early universe star formation bubble collision particle creation reheating white hole quasistar quasar feedback first stars nucleosynthesis hawking radiation mechanism first order phase transition phase transition analogy structure growth population iii stars critical collapse backreaction