Black holes Black holes An accretion disc (or accretion disk) is a structure formed by material falling into a gravitational source. Conservation of angular momentum requires that, as a large cloud of material collapses inward, any small rotation it may have will increase. Centrifugal force causes the rotating cloud to collapse into a disc, and tidal effects will tend to align this disc's rotation with the rotation of the gravitational source in the middle. Viscosity within the disc generates heat and saps orbital momentum, causing material in the disc to spiral inward until it impacts in an accretion shock on the central body if the body is a star, or slips toward the event horizon if the central body is a black hole. ...more on Wikipedia about "Accretion disc"
In theoretical physics, an AdS black hole is a black hole solution of general relativity or its extensions that asymptotically approaches anti de Sitter space at infinity. ...more on Wikipedia about "AdS black hole"
In general relativity, a black brane is a solution of the equations that generalizes a black hole solution but it is also extended - and translationally symmetric - in p additional spatial dimensions. Such a solution may therefore also be called a black p-brane. ...more on Wikipedia about "Black brane"
A black hole is a concentration of mass great enough that the force of gravity prevents anything from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). The gravitational field is so strong that the escape velocity near it exceeds the speed of light. This implies that nothing, not even light, can escape its gravity, hence the word "black". The term "black hole" is widespread, even though it does not refer to a hole in the usual sense, but rather a region of space from which nothing can return. ...more on Wikipedia about "Black hole"
In physics, there is a speculative notion that if there were a black hole with the same mass and charge as an electron, it would share many of the properties of the electron including the magnetic moment and Compton wavelength. ...more on Wikipedia about "Black hole electron"
Black hole entropy is entropy carried by a black hole. ...more on Wikipedia about "Black hole entropy"
The black hole information paradox results from the combination of quantum mechanics and general relativity. It was a contentious subject for science since it violated a commonly assumed tenet of science - that information cannot be destroyed. See Liouville's theorem (Hamiltonian) and unitary transformation. ...more on Wikipedia about "Black hole information paradox" Tell your friends about www.shortopedia.com
In physics a special field has been created entirely centered around the thermodynamics of black holes. Within black holes many of the physical laws which we accept should break down, including those of thermodynamics. ...more on Wikipedia about "Black hole thermodynamics"
The black string is a higher dimensional (D>4) generalization of a black hole in which the event horizon is topologically equivalent to S2 X S1 and spacetime is asypmtotically M(d-1) X S1. ...more on Wikipedia about "Black string"
A charged black hole is a black hole that possesses electric charge. Since the electromagnetic repulsion in compressing an electrically charged mass is dramatically greater than the gravitational attraction (by about 40 orders of magnitude), it is not expected that black holes with a significant electric charge will be formed in nature. ...more on Wikipedia about "Charged black hole"
In general relativity, the cosmic censorship hypothesis (CCH) is a conjecture about the nature of singularities in spacetime. ...more on Wikipedia about "Cosmic censorship hypothesis"
A dark-energy star or gravastar is a hypothetical compact astrophysical object which a minority of physicists feel might constitute an alternative explanation for observations of astronomical black hole candidates. ...more on Wikipedia about "Dark energy star"
An event horizon is a boundary in spacetime for a given observer beyond which no electromagnetic energy, including light, can reach the observer. ...more on Wikipedia about "Event horizon"
In theoretical physics, an extremal black hole is a black hole with the minimal possible mass that can be compatible with the given charges and angular momentum. ...more on Wikipedia about "Extremal black hole" My shortopedia is mine. shortopedia
In astrophysics, the Gravastar theory is a proposal by Pawel Mazur and Emil Mottola to replace the black hole. Instead of a star collapsing into a pinpoint of space with virtually infinite density, the gravastar theory proposes that as an object gravitationally collapses, space itself undergoes a phase transition preventing further collapse, being transformed into a spherical void surrounded by a form of super-dense matter. ...more on Wikipedia about "Gravastar"
Gravitational collapse in astronomy is the sudden inward fall of a massive body under the influence of the force of gravity. It occurs when all other forces fail to supply a sufficiently high pressure to counterbalance gravity and keep the massive body in (dynamical) equilibrium. Gravitational collapse is at the heart of the structure formation in the universe. An initial smooth distribution of matter will eventually collapse and cause the hierarchy of structures, such as clusters of galaxies, stellar groups, stars and planets. For example, a star is born through the gravitational collapse of a cloud of interstellar matter. The compression caused by the collapse raises the temperature until nuclear fuel ignites in the center of the star and the collapse comes to a halt. The thermal pressure gradient (leading to expansion) compensates the gravity (leading to compression) and a star is the dynamical equilibrium between these two forces. ...more on Wikipedia about "Gravitational collapse"
In physics, Hawking radiation is thermal radiation thought to be emitted by black holes due to quantum effects. It is named after British physicist Stephen Hawking who worked out the theoretical argument for its existence in 1974. Hawking's discovery became the first convincing insight in quantum gravity. However, the existence of Hawking radiation remains controversial. ** . ...more on Wikipedia about "Hawking radiation"
The holographic principle is a speculative conjecture about quantum gravity theories, proposed by Gerard 't Hooft and improved and promoted by Leonard Susskind, claiming that all of the information contained in a volume of space can be represented by a theory that lives in ...more on Wikipedia about "Holographic principle"
The Immirzi parameter (also known as the Barbero-Immirzi parameter) is a numerical coefficient appearing in loop quantum gravity, a nonperturbative theory of quantum gravity. The Immirzi parameter measures the size of the quantum of area in Planck units. As a result, its value is currently fixed by matching the semiclassical black hole entropy, as calculated by Stephen Hawking, and the counting of microstates in loop quantum gravity. ...more on Wikipedia about "Immirzi parameter"
An Intermediate-mass black hole (IMBH) is a black hole whose mass is significantly more than stellar black holes (a few tens of the mass of Sun) yet far less than supermassive black holes (a few millions of the mass of Sun). ...more on Wikipedia about "Intermediate-mass black hole"
In general relativity, the Kerr metric (or Kerr vacuum) describes the geometry of spacetime around a rotating massive body, such as a rotating black hole. This famous exact solution was discovered in 1963 by the New Zealand born mathematician Roy Kerr. ...more on Wikipedia about "Kerr metric"
The four laws of black hole mechanics are analogous to the laws of thermodynamics. ...more on Wikipedia about "Laws of black hole mechanics"
In black hole theory, the black hole membrane paradigm is a useful " toy model" method or "engineering approach" for visualising and calculating the effects predicted by quantum mechanics for the exterior physics of black holes, without using quantum-mechanical principles or calculations. It models a black hole as a thin classically-radiating surface (or membrane) at or vanishingly close to the black hole's event horizon. ...more on Wikipedia about "Membrane paradigm"
A micro black hole, also called a quantum mechanical black hole and inevitably a mini black hole, is simply a tiny black hole about which quantum mechanical effects play an important role. ...more on Wikipedia about "Micro black hole"
Microquasars are smaller cousins of quasars. They are named after quasars, as they have some common characteristics: strong and variable radio emission often seen as radio jets, and an accretion disk surrounding a black hole. In quasars, the black hole is supermassive (millions of solar masses) as in microquasars, the black hole mass is a few solar masses. In microquasars, the accreted mass comes from a normal star and the accretion disk is very luminous in optical regions and X-rays. Microquasars are sometimes called 'radio-jet X-ray binaries' to distinguish them from other X-ray binaries. A part of the radio emission comes from relativistic jets, often showing apparent superluminal motion. ...more on Wikipedia about "Microquasar"
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