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Bekenstein–Hawking Entropy Equation
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. Overview The second law of thermodynamics requires that black holes have entropy. If black holes carried no entropy, it would be possible to violate the second law by throwing mass into the black hole. The increase of the entropy of the black hole more than compensates for the decrease of the entropy carried by the object that was swallowed. In 1972, Jacob Bekenstein conjectured that black holes should have an entropy proportional to the area of the event horizon, where by the same year, he proposed no-hair theorems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Hole Merger
Black is a color that results from the absence or complete Absorption (electromagnetic radiation), absorption of visible spectrum, visible light. It is an achromatic color, without Colorfulness#Chroma, chroma, like white and grey. It is often used symbolically or figurative language, figuratively to represent darkness.Eva Heller, ''Psychologie de la couleur – effets et symboliques'', pp. 105–26. Black and white have often been used to describe opposites such as good and evil, the Dark Ages (historiography), Dark Ages versus the Age of Enlightenment, and night versus day. Since the Middle Ages, black has been the symbolic color of solemnity and authority, and for this reason it is still commonly worn by judges and magistrates. Black was one of the first colors used by artists in Neolithic cave paintings. It was used in ancient Egypt and Greece as the color of the underworld. In the Roman Empire, it became the color of mourning, and over the centuries it was frequently asso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Technology Review
''MIT Technology Review'' is a bimonthly magazine wholly owned by the Massachusetts Institute of Technology. It was founded in 1899 as ''The Technology Review'', and was re-launched without "''The''" in its name on April 23, 1998, under then publisher R. Bruce Journey. In September 2005, it was changed, under its then editor-in-chief and publisher, Jason Pontin, to a form resembling the historical magazine. Before the 1998 re-launch, the editor stated that "nothing will be left of the old magazine except the name." It was therefore necessary to distinguish between the modern and the historical ''Technology Review''. The historical magazine had been published by the MIT Alumni Association, was more closely aligned with the interests of MIT alumni, and had a more intellectual tone and much smaller public circulation. The magazine, billed from 1998 to 2005 as "MIT's Magazine of Innovation", and from 2005 onwards as simply "published by MIT", focused on new technology and how it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Near-extremal Black Hole
In theoretical physics, a near-extremal black hole is a black hole which is not far from the minimal possible mass that can be compatible with the given charges and angular momentum. The calculations of the properties of near-extremal black holes are usually performed using perturbation theory around the extremal black hole; the expansion parameter is called non-extremality. In supersymmetric theories, near-extremal black holes are often small perturbations of supersymmetric black holes. Such black holes have a very small Hawking temperature and consequently emit a small amount of Hawking radiation. Their black hole entropy can often be calculated in string theory In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. String theory describes how these strings propagate through space and intera ..., much like in the case of extremal black holes, at least to the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extremal Black Hole
In theoretical physics, an extremal black hole is a black hole with the minimum possible mass that is compatible with its charge and angular momentum. The concept of an extremal black hole is theoretical and none have thus far been observed in nature. However, many theories are based on their existence. In supersymmetric theories, extremal black holes are often supersymmetric: they are invariant under several supercharges. This is a consequence of the BPS bound. Such black holes are stable and emit no Hawking radiation. Their black hole entropy can be calculated in string theory. It has been suggested by Sean Carroll that the entropy of an extremal black hole is equal to zero. Carroll explains the lack of entropy by creating a separate dimension for the black hole to exist within. The Hawking radiation of extremal black holes is considered non-thermal (non-Planck distributed), with no associated temperature. The hypothetical black hole electron is super-extremal (having mor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
String Duality
String duality is a class of symmetries in physics that link different string theories, theories which assume that the fundamental building blocks of the universe are strings instead of point particles. Overview Before the so-called "duality revolution" there were believed to be five distinct versions of string theory, plus the (unstable) bosonic and gluonic theories. Note that in the type IIA and type IIB string theories closed strings are allowed to move everywhere throughout the ten-dimensional space-time (called the ''bulk''), while open strings have their ends attached to D-branes, which are membranes of lower dimensionality (their dimension is odd - 1,3,5,7 or 9 - in type IIA and even - 0,2,4,6 or 8 - in type IIB, including the time direction). Before the 1990s, string theorists believed there were five distinct superstring theories: type I, types IIA and IIB, and the two heterotic string theories ( SO(32) and ''E''8×''E''8). The thinking was that out of these fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
D-branes
In string theory, D-branes, short for Dirichlet membrane, are a class of extended objects upon which open string (physics), strings can end with Dirichlet boundary conditions, after which they are named. D-branes are typically classified by their spatial dimension, which is indicated by a number written after the ''D.'' A D0-brane is a single point, a D1-brane is a line (sometimes called a "D-string"), a D2-brane is a plane, and a D25-brane fills the highest-dimensional space considered in bosonic string theory. There are also instantonic D(−1)-branes, which are localized in both space and time. Discovery D-branes were discovered by Jin Dai, Robert Leigh (physicist), Robert Leigh, and Joseph Polchinski, and independently by Petr Hořava (physicist), Petr Hořava, in 1989. In 1995, Polchinski identified D-branes with black p-brane solutions of supergravity, a discovery that triggered the Second Superstring Revolution, second superstring revolution and led to both Holographic pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
String Theory
In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. String theory describes how these strings propagate through space and interact with each other. On distance scales larger than the string scale, a string acts like a particle, with its mass, charge, and other properties determined by the vibrational state of the string. In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries the gravitational force. Thus, string theory is a theory of quantum gravity. String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics. String theory has contributed a number of advances to mathematical physics, which have been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, and condensed matter ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersymmetry
Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It proposes that for every known particle, there exists a partner particle with different spin properties. There have been multiple experiments on supersymmetry that have failed to provide evidence that it exists in nature. If evidence is found, supersymmetry could help explain certain phenomena, such as the nature of dark matter and the hierarchy problem in particle physics. A supersymmetric theory is a theory in which the equations for force and the equations for matter are identical. In theoretical physics, theoretical and mathematical physics, any theory with this property has the ''principle of supersymmetry'' (SUSY). Dozens of supersymmetric theories exist. In theory, supersymmetry is a type of Spacetime symmetries, spacetime symmetry betwe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cumrun Vafa
Cumrun Vafa (, ; born 1 August 1960) is an Iranian-American theoretical physicist and the Hollis Professor of Mathematicks and Natural Philosophy at Harvard University. Early life and education Cumrun Vafa was born in Tehran, Iran on 1 August 1960. He became interested in physics as a young child, specifically how the moon was not falling from the sky, and he later grew his interests in math by high school and was fascinated by how mathematics could predict the movement of objects. He graduated from Alborz High School in Tehran and moved to the United States in 1977 to study at university. He received a B.S. in mathematics and physics from the Massachusetts Institute of Technology (MIT) in 1981. He received his Ph.D. in physics from Princeton University in 1985 after completing a doctoral dissertation, titled "Symmetries, inequalities and index theorems", under the supervision of Edward Witten. Academia After his PhD degree, Vafa became a junior fellow via the Harvard Soc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andrew Strominger
Andrew Eben Strominger (; born 1955) is an American theoretical physicist who is the director of Harvard's Center for the Fundamental Laws of Nature. He has made significant contributions to quantum gravity and string theory. These include his work on Calabi–Yau compactification and topology change in string theory, and on the stringy origin of black hole entropy. He is a senior fellow at the Society of Fellows, and is the Gwill E. York Professor of Physics. Education Strominger received his bachelor's degree at Harvard College in 1977 and his master's degree at the University of California, Berkeley. He then received his PhD at MIT in 1982 under the supervision of Roman Jackiw. Prior to joining Harvard as a professor in 1997, he held a faculty position at the University of California, Santa Barbara. He is the author of over 200 publications. Research Notable contributions * a paper with Cumrun Vafa that explains the microscopic origin of the black hole entropy, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ryu–Takayanagi Conjecture
Shinsei Ryu and Tadashi Takayanagi published 2006 a conjecture within holography that posits a quantitative relationship between the entanglement entropy of a conformal field theory and the geometry of an associated anti-de Sitter spacetime. The formula characterizes "holographic screens" in the bulk; that is, it specifies which regions of the bulk geometry are "responsible to particular information in the dual CFT". The authors were awarded the 2015 Breakthrough Prize in Fundamental Physics for "fundamental ideas about entropy in quantum field theory and quantum gravity", and awarded the 2024 Dirac Medal of the ICTP for "their insights on quantum entropy in quantum gravity and quantum field theories". The formula was generalized to a covariant form in 2007. Motivation The thermodynamics of black holes suggests certain relationships between the entropy of black holes and their geometry. Specifically, the Bekenstein–Hawking area formula conjectures that the entropy of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bekenstein Bound
In physics, the Bekenstein bound (named after Jacob Bekenstein) is an upper limit on the thermodynamic entropy ''S'', or Shannon entropy ''H'', that can be contained within a given finite region of space which has a finite amount of energy—or conversely, the maximum amount of information that is required to perfectly describe a given physical system down to the quantum level. It implies that the information of a physical system, or the information necessary to perfectly describe that system, must be finite if the region of space and the energy are finite. Equations The universal form of the bound was originally found by Jacob Bekenstein in 1981 as the inequality S \leq \frac, where ''S'' is the entropy, ''k'' is the Boltzmann constant, ''R'' is the radius of a sphere that can enclose the given system, ''E'' is the total mass–energy including any rest masses, ''ħ'' is the reduced Planck constant, and ''c'' is the speed of light. Note that while gravity plays a significant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
