Scientists Find Theoretical Possibility of Rapidly Spinning Black Holes Splitting in Two

A new theoretical study suggests that a black hole could, under exceptionally restrictive conditions, split into two smaller black holes rather than only merge with another black hole. The researchers found that extremely rapid rotation may create a narrow possibility for this process, although the conditions needed for the two fragments to separate make it difficult.

The research, published in Physical Review D on October 22, 2026, does not report an observed black hole splitting or demonstrate that the process occurs in nature. Instead, it examines the thermodynamic and physical constraints that normally prevent black holes from fragmenting, and identifies circumstances in which those barriers might be overcome.

Key Takeaways

• Researchers have examined whether a single black hole could fragment into two smaller black holes.
• Extremely rapid rotation may create a narrow theoretical possibility for splitting.
• The resulting black holes must have enough energy and momentum to separate instead of falling back together.
• The study’s calculations suggest that the possibility is restricted to black holes rotating close to their maximum theoretical rate.
• The researchers also investigate fragmentation in higher-dimensional and modified-gravity scenarios.
• Small primordial black holes may be more susceptible to certain fragmentation mechanisms.
• No black hole splitting event has been observed or confirmed.

Why Black Holes Do Not Normally Split

Black holes are generally known for merging. When two black holes collide, they can combine into a larger black hole while releasing energy in the form of gravitational waves.

The reverse process presents a much bigger challenge.

One of the main reasons is a physical property called entropy. In simple terms, entropy measures the number of microscopic arrangements associated with a physical system.

Black holes also have entropy, which is closely connected to the area of their event horizons. Under the standard description of a non-rotating black hole, dividing one large black hole into two smaller ones would reduce the combined entropy.

That reduction conflicts with the classical area theorem, which states that the total area of black hole event horizons cannot decrease under the assumptions of classical general relativity.

This makes ordinary black hole fragmentation thermodynamically unfavourable.

The new research investigates whether rotation or changes to the underlying gravitational framework could create exceptions.

Extreme Rotation Could Create a Narrow Opening

The researchers found that rotation changes the thermodynamic calculations.

A rotating black hole has different entropy properties from a non-rotating one with the same mass. Its angular momentum creates an opportunity for some of that rotational energy to be converted into the orbital motion of two possible fragments.

This could improve the entropy balance and make a split appear more favourable under certain conditions.

However, passing the entropy test is not enough.

The two resulting black holes would need to move far enough apart to avoid immediately falling back together. That requires sufficient energy and angular momentum.

When the researchers included these additional requirements, the range of possible splitting conditions became much narrower.

Their analysis suggests that the process might be allowed only when the original black hole rotates extremely close to its maximum possible rate.

This is a theoretical possibility within the study’s simplified framework, not evidence that rapidly spinning black holes actually break apart.

What Is a Pair-of-Pants Topology?

The study has an unusual title: When Black Holes Admit Pair-of-pants Topologies.

The phrase describes the hypothetical shape of the event horizon through time if a single black hole divided into two.

An event horizon is the boundary beyond which nothing, including light, can escape a black hole’s gravitational pull.

If one black hole split into two, its horizon would begin as a single connected structure and then branch into two separate structures. When represented across spacetime, this shape resembles a pair of trousers.

Part of the shape	What it represents
Upper section	The original black hole
Narrow connecting region	The hypothetical transition
Two lower branches	The two resulting black holes

The term is a mathematical description of the proposed spacetime geometry. It does not mean that a black hole physically changes into a clothing-like shape.

The researchers use this framework to examine whether the geometry and physical conditions associated with fragmentation are compatible with known constraints.

Researchers Also Investigate Extra Dimensions

The study goes beyond rapidly rotating black holes in ordinary four-dimensional spacetime.

It also examines more exotic possibilities involving theories with additional spatial dimensions.

One example is the Gregory-Laflamme instability, which can affect extended black-hole-like objects called black strings in higher-dimensional theories.

Under certain conditions, these objects can become unstable and develop uneven structures that may lead to fragmentation-like behaviour.

The researchers also discuss other possibilities involving superradiant instabilities and modified theories of gravity.

These models can change the relationship between a black hole’s mass, horizon size and entropy. In some cases, producing a much smaller fragment alongside a larger black hole can become thermodynamically favourable.

However, a favourable entropy calculation does not prove that a physical splitting process will occur. The system must also satisfy the relevant energy, momentum and spacetime constraints.

These scenarios remain theoretical and should not be confused with confirmed behaviour of ordinary astrophysical black holes.

Could Scientists Detect a Black Hole Splitting?

The researchers say small primordial black holes could be particularly interesting.

Primordial black holes are hypothetical objects that may have formed in the early universe, rather than through the collapse of massive stars.

Some theoretical models suggest that smaller black holes could be more susceptible to fragmentation-related effects than much larger astrophysical black holes.

The team also discusses the possibility of detecting tiny black-hole fragments indirectly through gamma-ray signals.

If such fragments formed, they could potentially lose mass through Hawking radiation, a theoretical process in which black holes emit radiation and gradually lose energy.

Gamma-ray observatories such as NASA’s Fermi Large Area Telescope (Fermi-LAT) could search for signals associated with these hypothetical fragments.

However, no such signal has been identified as evidence of black hole fragmentation. The researchers also say they cannot yet provide a single probability for how often splitting might happen.

That probability depends on how gravity behaves under the extreme conditions involved and whether the proposed fragmentation mechanisms can occur dynamically.

The Bigger Picture

The research challenges the assumption that black holes can only grow through mergers, but it does not overturn established physics.

Instead, it identifies narrow theoretical circumstances in which fragmentation might be possible and explains why the process remains difficult to achieve.

The study is also important because it connects black hole thermodynamics, spacetime geometry and alternative theories of gravity. Understanding these connections could help physicists investigate whether Einstein’s general relativity describes every aspect of gravity under the most extreme conditions.

Looking Ahead

The next step is to determine whether the theoretical conditions identified in the study can produce an actual black hole splitting event through a physically consistent process. Researchers will need to investigate the underlying gravitational dynamics, calculate possible probabilities and identify observational signatures that distinguish fragmentation from other astrophysical events.

For astronomers, gamma-ray observations and future studies of primordial black holes could provide ways to test some of these predictions. Until there is stronger theoretical or observational evidence, black hole splitting remains an intriguing possibility rather than an established cosmic phenomenon.