Dark matter might be made of 'runaway' black holes that started smaller than an atom.
April 17, 2026
Original Paper
Microscopic primordial black holes as macroscopic dark matter from large extra dimensions
arXiv · 2604.14871
The Takeaway
We have long suspected black holes could be dark matter, but we couldn't figure out where the 'mid-sized' ones came from. This theory suggests that if there are extra dimensions in space, tiny microscopic black holes from the Big Bang could have gorged themselves on energy. They would have grown from sub-atomic sizes to the mass of our Sun in the blink of an eye. This explains why we can't find dark matter particles—it is because they aren't particles, but 'inflated' black holes hiding in plain sight. It turns the hunt for dark matter into a search for these ancient, invisible giants.
From the abstract
We study the coupled cosmological evolution of primordial black holes (PBHs) and radiation in the Arkani-Hamed-Dimopoulos-Dvali (ADD) framework with $n$ large extra dimensions and a fundamental gravity scale $M_\star$ at the TeV scale. For PBHs with horizon radius smaller than the compactification scale, the higher-dimensional geometry implies a larger horizon size at fixed mass and therefore a suppressed Hawking temperature. As a result, radiation accretion can overcome evaporation in the early