The very first black holes in the universe formed in a repeating, fractal-like pattern that looks the same at every scale.
April 29, 2026
Original Paper
Cosmological discrete self-similarity in primordial black hole formation
arXiv · 2604.21520
The Takeaway
Primordial black holes formed during the expansion of the early universe exhibit a phenomenon called discrete self-similarity. This means the way they collapsed followed a mathematical rhythm that produced log-periodic oscillations. These repeating patterns are common in nature, from the shapes of coastlines to the growth of trees, but seeing them in cosmic collapse is unexpected. This fractal signature could still be echoing through the universe in the form of specific gravitational waves. If detected, these echoes would provide a direct window into the conditions of the universe just moments after the Big Bang.
From the abstract
We demonstrate that discrete self-similarity (DSS), originally discovered in the collapse of a massless scalar field in an asymptotically flat system, survives in primordial black hole (PBH) formation within an expanding cosmological background. Using fully relativistic numerical simulations of massless scalar-field collapse in an Friedmann-Lemaître-Robertson-Walker universe, we resolve the critical regime down to $|p-p_c|\sim 10^{-8}$, where $p$ and $p_c$ respectively are a parameter of the fam