Traditional black holes, as predicted by Albert Einstein’s theory of General Relativity, contain what are known as
singularities, i.e. points where the laws of physics break down. Identifying how singularities are resolved in the context of quantum gravity is one of the fundamental problems in theoretical physics. Now, a team of experts from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) has described for the first time the creation of regular black holes from gravitational effects and without the need for the existence of exotic matter required by some previous models.
This discovery, published in the journal Physics Letters B, opens up new prospects for improving our understanding of the quantum nature of gravity and the true structure of space-time.
Black holes without singularities
The term exotic matter refers to a type of matter that has unusual properties not found in ordinary matter. It often has a negative energy density, creates repulsive gravitational effects, and can violate certain energy conditions in general relativity. Exotic matter is largely theoretical and has not been observed in nature, but is used in models to explore concepts such as wormholes, faster-than-light travel and the resolution of black hole singularities.
The new study mathematically demonstrates that an infinite series of higher-order gravitational corrections can eliminate these singularities and result in so-called regular black holes.
Unlike previous models, which required exotic matter, this new study reveals that pure gravity — without additional matter fields — can generate regular black holes without singularities.
This discovery represents a significant departure from previous theories and simplifies the conditions necessary for regular black holes.
“The beauty of our construction is that it is based only on modifications of the Einstein equations predicted naturally by quantum gravity. No other components are needed”, says researcher Pablo A. Cano, from the Department of Quantum Physics and Astrophysics at the Faculty of Physics and ICCUB.
The theories deployed by the ICCUB team are applicable to any dimension of space-time greater than or equal to five. “The reason for considering higher space-time dimensions is purely technical”, says Cano, “as it allows us to reduce the mathematical complexity of the problem”. However, the researchers say that “the same conclusions should apply to our four-dimensional space-time”.
“Most scientists agree that the singularities of general relativity must ultimately be resolved, although we know very little about how this process might be achieved. Our work provides the first mechanism to achieve this in a robust way, albeit under certain symmetry assumptions”, explains Robie Hennigar (UB and ICCUB). “It is not yet clear how nature prevents the formation of singularities in the universe, but we hope that our model will help us to gain a better understanding of this process”, says the expert.
Exploring discoveries in astrophysical scenarios
The study also explores the thermodynamic properties of these regular black holes and reveals that they comply with the first law of thermodynamics. The theories developed provide a robust framework for understanding the thermodynamics of black holes in a completely universal and unambiguous way. This consistency adds credibility and potential applicability to the findings.
The researchers plan to extend their work to four-dimensional space-time and explore the implications of their findings in various astrophysical scenarios. They also aim to investigate the stability and possible observational signatures of these regular black holes.
“These theories not only predict singularity-free black holes, but also allow us to understand how these objects form and what is the fate of matter falling into a black hole. We are already working on these questions and expect to find really exciting results”, concludes Cano.