A black hole is a region of spacetime where gravity is so strong that nothing,not even light and other electromagnetic waves,is capable of possessing enough energy to escape it. Einstein's theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. A black hole has a great effect on the fate and circumstances of an object crossing it,but it has no locally detectable features according to general relativity. In many ways,a black hole acts like an ideal black body,as it reflects no light. Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation,with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes,making it essentially impossible to observe directly.
General relativity,also known as the general theory of relativity,and as Einstein's theory of gravity,is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation,providing a unified description of gravity as a geometric property of space and time,or four-dimensional spacetime. In particular,the curvature of spacetime is directly related to the energy and momentum of whatever present matter and radiation. The relation is specified by the Einstein field equations,a system of second-order partial differential equations.
In general relativity,a naked singularity is a hypothetical gravitational singularity without an event horizon.
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics. It deals with environments in which neither gravitational nor quantum effects can be ignored,such as in the vicinity of black holes or similar compact astrophysical objects,as well as in the early stages of the universe moments after the Big Bang.
A wormholeis a hypothetical structure connecting disparate points in spacetime,and is based on a special solution of the Einstein field equations.
The following is a timeline of gravitational physics and general relativity.
In physics,black hole thermodynamics is the area of study that seeks to reconcile the laws of thermodynamics with the existence of black hole event horizons. As the study of the statistical mechanics of black-body radiation led to the development of the theory of quantum mechanics,the effort to understand the statistical mechanics of black holes has had a deep impact upon the understanding of quantum gravity,leading to the formulation of the holographic principle.
Jorge Pullin is an Argentine-American theoretical physicist known for his work on black hole collisions and quantum gravity. He is the Horace Hearne Chair in theoretical Physics at the Louisiana State University.
A gravastar is an object hypothesized in astrophysics by Pawel O. Mazur and Emil Mottola as an alternative to the black hole theory. It has usual black hole metric outside of the horizon,but de Sitter metric inside. On the horizon there is a thin shell of matter. The term "gravastar" is a portmanteau of the words "gravitational vacuum star". Further theoretical considerations of gravastars include the notion of a nestar.
Micro black holes,also called mini black holes or quantum mechanical black holes,are hypothetical tiny black holes,for which quantum mechanical effects play an important role. The concept that black holes may exist that are smaller than stellar mass was introduced in 1971 by Stephen Hawking.
The black hole information paradox is a paradox that appears when the predictions of quantum mechanics and general relativity are combined. The theory of general relativity predicts the existence of black holes that are regions of spacetime from which nothing—not even light—can escape. In the 1970s,Stephen Hawking applied the semiclassical approach of quantum field theory in curved spacetime to such systems and found that an isolated black hole would emit a form of radiation. He also argued that the detailed form of the radiation would be independent of the initial state of the black hole,and depend only on its mass,electric charge and angular momentum.
In theoretical physics,quantum field theory in curved spacetime (QFTCS) is an extension of quantum field theory from Minkowski spacetime to a general curved spacetime. This theory uses a semi-classical approach;it treats spacetime as a fixed,classical background,while giving a quantum-mechanical description of the matter and energy propagating through that spacetime. A general prediction of this theory is that particles can be created by time-dependent gravitational fields (multigraviton pair production),or by time-independent gravitational fields that contain horizons. The most famous example of the latter is the phenomenon of Hawking radiation emitted by black holes.
Numerical relativity is one of the branches of general relativity that uses numerical methods and algorithms to solve and analyze problems. To this end,supercomputers are often employed to study black holes,gravitational waves,neutron stars and many other phenomena described by Albert Einstein's theory of general relativity. A currently active field of research in numerical relativity is the simulation of relativistic binaries and their associated gravitational waves.
A ring singularity or ringularity is the gravitational singularity of a rotating black hole,or a Kerr black hole,that is shaped like a ring.
In astrophysics,an extreme mass ratio inspiral (EMRI) is the orbit of a relatively light object around a much heavier object,that gradually spirals in due to the emission of gravitational waves. Such systems are likely to be found in the centers of galaxies,where stellar mass compact objects,such as stellar black holes and neutron stars,may be found orbiting a supermassive black hole. In the case of a black hole in orbit around another black hole this is an extreme mass ratio binary black hole. The term EMRI is sometimes used as a shorthand to denote the emitted gravitational waveform as well as the orbit itself.
Gary T. Horowitz is an American theoretical physicist who works on string theory and quantum gravity.
Carlos O. Lousto is a Distinguished Professor in the School of Mathematical Sciences in Rochester Institute of Technology,known for his work on black hole collisions.
Manuela Campanelli is a distinguished professor of astrophysics of the Rochester Institute of Technology. She also holds the John Vouros endowed professorship at RIT and is the director of its Center for Computational Relativity and Gravitation. Her work focuses on the astrophysics of merging black holes and neutron stars,which are powerful sources of gravitational waves,electromagnetic radiation and relativistic jets. This research is central to the fields of relativistic astrophysics and gravitational-wave astronomy.
Infinite derivative gravity is a theory of gravity which attempts to remove cosmological and black hole singularities by adding extra terms to the Einstein–Hilbert action,which weaken gravity at short distances.
In quantum gravity and quantum complexity theory,the complexity equals action duality (CA-duality) is the conjecture that the gravitational action of any semiclassical state with an asymptotically anti-de Sitter background corresponds to quantum computational complexity,and that black holes produce complexity at the fastest possible rate. In technical terms,the complexity of a quantum state on a spacelike slice of the conformal field theory dual is proportional to the action of the Wheeler–DeWitt patch of that spacelike slice in the bulk. The WDW patch is the union of all possible spacelike slices of the bulk with the CFT slice as its boundary.
