There is a strict physical "speed limit" on how big a black hole can actually grow.
April 14, 2026
Original Paper
Finite Hilbert space and maximum mass of Schwarzschild black holes from a Generalized Uncertainty Principle
arXiv · 2604.08953
The Takeaway
By applying quantum uncertainty rules, researchers found that black holes have a maximum mass and a specific "staircase" of allowed sizes. This gives astronomers a definitive limit to look for when observing the monster black holes at the centers of galaxies.
From the abstract
We show that implementing a generalized uncertainty principle (GUP) with both minimal length and maximal momentum directly on the reduced phase space of the Schwarzschild black hole (BH) leads to a finite and discrete mass spectrum, a strict upper bound on the BH mass, a bounded entropy, and a fully regulated Hawking temperature. We further construct a GUP-deformed lapse function that preserves the ADM mass and horizon radius while exactly reproducing the GUP temperature through the surface grav