Black holes can exist without a central singularity
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SUPPORTED
the evidence backs this
refutedsupported
the weight of evidence
5 sources for · 2 against
Peer-reviewed literature in theoretical physics explores theoretical and regular black hole models in frameworks beyond standard general relativity that bypass central singularities.
General relativity predicts the presence of a singularity inside of a black hole revealing that it is not a complete theory of gravity. A real structure of a black hole interior near an expected singularity depends on the UV completion of gravity. In this paper we address the question of whether singular spherically symmetric solutions are absent (or present) in a complete gravity theory. We find that the answer is governed by the functional form of a nonperturbative graviton propagator. A ghost-free infinite derivative gravity is favored by the unitarity the graviton propagator of an exponential form. We explicitly show in this framework that a singularity is not possible unless an unphysical situation when a mass of the black hole is infinite is considered.
change. General relativity also predicts that every black hole should have a central singularity, where the curvature of spacetime is infinite. Objects
A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Albert Einstein's theory of general relativity, which describes gravitation as the curvature of spacetime, predicts that any sufficiently compact mass will form a black hole. The boundary of no escape is called the event horizon. In general relativity, crossing a black hole's event h
A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Albert Einstein's theory of general relativity, which describes gravitation as the curvature of spacetime, predicts that any sufficiently compact mass will form a black hole. The boundary of no escape is called the event horizon. In general relativity, crossing a black hole's event horizon traps an object inside but produces no locally detectable change. General relativity also predicts that every black hole should have a central singularity, where the curvature of spacetime is infinite.
Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century. In 1916, the first solution of general relativity that would characterise a black hole was found. By the late 1950s, this solution began to be interpreted physically as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The first widely accepted black hole was Cygnus X-1, an x-ray source proposed as a black hole binary through several studies between 1971 and 1974.
Black holes typically form as part of a supernova event when massive stars collapse at the end of their life cycle. After a black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses may form by absorbing stars and merging with other black holes, or via direct collapse of gas clouds. There is consensus that supermassive black holes exist in the centres of most galaxies.
Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the rate of emission being inversely proportional to the mass. This causes the black hole to lose mass very slowly, provided it is not accreting matter. However, even the smallest class of black holes observed, stellar black holes, are gaining mass from the cosmic microwave background faster than they are losing mass via Hawking radiation.
The presence of a black hole can be inferred through its…
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Abstract Black hole solutions in general relativity come with pathologies such as singularity and mass inflation instability, which are believed to be cured by a yet-to-be-found quantum theory of gravity. Without such consistent description, one may model theory-agnostic phenomenological black holes that bypass the aforesaid issues. These so-called regular black holes are extensively studied in the literature using parameterized modifications over the black hole solutions of general relativity. However, since there exist several ways to model such black holes, it is important to study the consistency and viability of these solutions from both theoretical and observational perspectives. In this work, we consider a recently proposed model of regularized stable rotating black holes having two extra parameters in addition to the mass and spin of a Kerr solution. We start by computing their quasi-normal modes under scalar perturbation and investigate the impact of those additional parameters on black hole stability. In the second part, we study shadows of the central compact objects in $$M87^*$$ M 87 ∗ and $$Sgr\, A^*$$ S g r A ∗ modelled by these regularized black holes and obtain stringent bounds on the parameter space requiring consistency with Event Horizon Telescope observations.
The 1965 Penrose singularity theorem demonstrates the utterly inevitable and unavoidable formation of spacetime singularities under physically reasonable assumptions, and it remains one of the main results in our understanding of black holes. It is standard lore that quantum gravitational effects will always tame these singularities in black hole interiors. However, the Penrose's theorem provides no clue as to the possible (non-singular) geometries that may be realized in theories beyond general relativity as the result of singularity regularization. In this paper we analyze this problem in spherically symmetric situations, being completely general otherwise, in particular regarding the dynamics of the gravitational and matter fields. Our main result is that, contrary to what one might expect, the set of regular geometries that arises is remarkably limited. We rederive geometries that have been analyzed before, but also uncover some new possibilities. Moreover, the complete catalogue of possibilities that we obtain allows us to draw the novel conclusion that there is a clear tradeoff between internal and external consistency: One has to choose between models that display internal inconsistencies, or models that include significant deviations with respect to general relativity, which should therefore be amenable to observational tests via multi-messenger astrophysics.
A black hole arises from the gravitational collapse of a massive stellar object, such as a massive star or remnants of a supernova. When the internal nuclear fusion reactions that sustain a star's energy cease, the inward gravitational pull overwhelms the outward pressure generated by the star's core.While our current understanding of black holes includes a singularity at their core, it is interesting to explore a speculative model of a black hole without a singularity.One possible approach is to consider the concept of a "regular" or "nonsingular" black hole. In this model, instead of a singularity, the central region of the black hole would be occupied by a highly dense but finite region of matter or energy. This central region would be subject to extreme gravitational forces but would not collapse to an infinitely small point.The exact nature of this central region could be described by a modified theory of gravity, which would account for the effects of strong gravitational fields while preventing the formation of a singularity. Such a theory would need to reconcile the behavior of gravity at both small and large scales.While speculative and currently lacking empirical evidence, models like these suggest alternative possibilities for the nature of black holes. They are areas of active research in theoretical physics and may help us better understand the extreme conditions that exist within these enigmatic cosmic objects.
Black holes and Rindler superspace: classical singularity and quantum unitarity
Canonical quantization of spherically symmetric initial data which is appropriate to classical interior black hole solutions in four dimensions is carried out and solved exactly without gauge fixing the remaining kinematic Gauss Law constraint. The resultant mini-superspace manifold and arena for quantum geometrodynamics is two-dimensional, of signature (+, -), non-singular, and can in fact be identified precisely with the first Rindler wedge. The associated Wheeler-DeWitt equation with evolution in intrinsic superspace time can be formulated as a free massive Klein-Gordon equation; and the Hamilton-Jacobi semiclassical limit of plane wave solutions can be matched precisely to the interiors of Schwarzschild black holes. Furthermore, classical black hole horizons and singularities correspond to the boundaries of the Rindler wedge. Exact wavefunctions of the first-order-in-superspace intrinsic time Dirac equation are also considered. Precise correspondence between Schwarzschild black holes and free particle mechanics in superspace is noted.
When asked to discuss Cyg XR-1, E. E. Salpeter once concluded, 'A black hole in Cyg X(R)-1 is the most conservative hypothesis.' Recent observations now make it likely that a black hole in Cyg XR-1 is the only hypothesis tenable. Chandrasekhar first showed that compact stars - those with the inward force of gravity on their outer layers balanced by the pressure generated by the Pauli exclusion principle acting on its electrons (in white dwarfs) or nucleons (in neutron stars) - have a maximum mass. Equilibrium is achieved at a minimum of the total energy of the star, which is the sum of the positive Fermi energy and the negative gravitational energy. The maximum mass attainable in equilibrium is found by setting E = 0: M(max) = 1.5 M(Sun). If the mass of the star is larger than this, then E can be decreased without bound by decreasing the star's radius and increasing its (negative) gravitational energy. No equilibrium value of the radius exist, and general relativity predicts that gravitational collapse to a point occurs. This point singularity is a black hole.
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