Some black holes could have negative mass instead of being heavy monsters of gravity.
April 20, 2026
Original Paper
Zero-Mass Rotating Spacetimes in Four-Dimensional Hoúva Gravity
SSRN · 6603300
The Takeaway
Standard physics says that black holes are formed from massive amounts of matter crushed into a tiny point. This research into Hoúva gravity shows that it is possible to have a rotating spacetime with zero or even negative mass. These objects still possess an ergosphere, a region that can drag space around them, and they still emit heat. This contradicts the fundamental intuition that gravity only comes from positive weight. If these objects exist, they would represent a completely new class of celestial bodies that do not follow the rules of General Relativity. This discovery opens the door to a universe where gravity can behave in ways we never imagined.
From the abstract
We study a particular exact solution for rotating spacetimes in four-dimensional Hoˇrava gravity, which has been proposed as a renormalizable gravity model without the ghost problem. We show that the zero-mass Kerr spacetime or the zero-mass Kerr-(A)dS spacetime in Einstein gravity is an exact solution in four-dimensional Hoˇrava for an arbitrary IR Lorentz-violation parameter λ, but with an appropriate cosmological constant. In particular, for the zero-mass topological Kerr-AdS black hole solut