In 1965, British mathematician Roger Penrose proposed the cosmic censorship conjecture, a concept that suggests that singularities—regions where gravity is so strong that the fabric of spacetime breaks—can never be viewed as they remain hidden behind the event horizon of black holes.

Penrose won the 2020 Nobel Prize for his work that describes that singularities are the unique points in spacetime where classical laws of physics such as general relativity don’t work.

However, while Penrose’s description of black hole singularities is widely respected and accepted among physicists, until now, there has been no mathematical evidence to prove the cosmic censorship conjecture.

Finally, a study reveals a new model that provides a solid mathematical basis for the hidden nature of singularities in quantum black holes. The study authors suggest that their findings could solve many mysteries associated with quantum gravity.

Decoding quantum cosmic censorship

Unlike classical black holes, quantum black holes are tiny subatomic structures that are driven by the rules of both quantum mechanics and general relativity. While regular black holes are formed due to the collapse of massive stars, quantum black holes can be created in a particle accelerator such as the large Hadron collider.

However, scientists have found strong evidence indicating the presence of classical black holes in outer space, whereas quantum black holes remain a theoretical concept to this date.

Considering their theoretical nature, the study authors developed a model that checks whether the singularities of quantum black holes remain shielded when quantum matter interacts with them. This model uses gravitational holography, an approach that helps scientists understand the effect of gravity in extreme conditions such as those found inside a black hole.

Using the holography method, the information about a black hole can be encoded on its boundary (the event horizon), similar to how a hologram contains 3D information in a 2D image.

The results from the model suggest that when quantum matter is introduced in spacetime geometries, due to the quantum effect, an event horizon forms around a naked singularity—completely hiding it from view.

Since this effect is observed on the quantum scale, it is referred to as quantum cosmic censorship. “This process—quantum effects modifying the initial classical geometry to clothe a singularity—intuitively captures the spirit of cosmic censorship, but it is solely a quantum effect. And so it is dubbed ‘quantum’ cosmic censorship,” Andrew Svesko, one of the study authors and a research associate at King’s College, London, said.

A test bed for quantum gravity

While scientists have yet to provide mathematical evidence for cosmic censorship in classical physics, the new model would work as an important stepping stone in this direction. Plus, it will help scientists unravel concepts such as quantum gravity.

“Resolving black hole singularities continues to be a chief goal for quantum gravity; thus, rigorously understanding how notions like cosmic censorship and the Penrose inequality behave when quantum matter effects are accounted for adds to the list of criteria that can be used to further develop quantum gravity,” Svesko added.

Moreover, apart from cosmic censorship, the new model also reveals ways to understand black hole entropy, the degree of randomness in black holes. Hopefully, the model will bring us closer to gaining in-depth knowledge of many other intriguing properties of black holes.

The study is published in the journal Physical Review Letters.