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CGh Physics
''cGh'' physics refers to the historical attempts in physics to unify relativity, gravitation and quantum mechanics, in particular following the ideas of Matvei Petrovich Bronstein and George Gamow. The letters are the standard symbols for the speed of light (''c''), the gravitational constant (''G''), and Planck constant, Planck's constant (''h''). If one considers these three universal constants as the basis for a 3-D coordinate system and envisions a cube, then this pedagogic construction provides a framework, which is referred to as the ''cGh'' cube, or physics cube, or cube of theoretical physics (CTP). This cube can used for organizing major subjects within physics as occupying each of the eight corners. The eight corners of the ''cGh'' physics cube are: * Classical mechanics (_, _, _) * Special relativity (''c'', _, _), gravitation (_, ''G'', _), quantum mechanics (_, _, ''h'') * General relativity (''c'', ''G'', _), quantum field theory (''c'', _, ''h''), non-relativistic q ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Gravity
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, such as neutron stars. Three of the four fundamental forces of physics are described within the framework of quantum mechanics and quantum field theory. The current understanding of the fourth force, gravity, is based on Albert Einstein's general theory of relativity, which is formulated within the entirely different framework of classical physics. However, that description is incomplete: describing the gravitational field of a black hole in the general theory of relativity leads physical quantities, such as the spacetime curvature, to diverge at the center of the black hole. This signals the breakdown of the general theory of relativity and the need for a theory that goes b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Gravity
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, such as neutron stars. Three of the four fundamental forces of physics are described within the framework of quantum mechanics and quantum field theory. The current understanding of the fourth force, gravity, is based on Albert Einstein's general theory of relativity, which is formulated within the entirely different framework of classical physics. However, that description is incomplete: describing the gravitational field of a black hole in the general theory of relativity leads physical quantities, such as the spacetime curvature, to diverge at the center of the black hole. This signals the breakdown of the general theory of relativity and the need for a theory that goes b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conjugate Variables
Conjugate variables are pairs of variables mathematically defined in such a way that they become Fourier transform duals, or more generally are related through Pontryagin duality. The duality relations lead naturally to an uncertainty relation—in physics called the Heisenberg uncertainty principle—between them. In mathematical terms, conjugate variables are part of a symplectic basis, and the uncertainty relation corresponds to the symplectic form. Also, conjugate variables are related by Noether's theorem, which states that if the laws of physics are invariant with respect to a change in one of the conjugate variables, then the other conjugate variable will not change with time (i.e. it will be conserved). Examples There are many types of conjugate variables, depending on the type of work a certain system is doing (or is being subjected to). Examples of canonically conjugate variables include the following: * Time and frequency: the longer a musical note is sustained, the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commutation Relation
In mathematics, the commutator gives an indication of the extent to which a certain binary operation fails to be commutative. There are different definitions used in group theory and ring theory. Group theory The commutator of two elements, and , of a group , is the element : . This element is equal to the group's identity if and only if and commute (from the definition , being equal to the identity if and only if ). The set of all commutators of a group is not in general closed under the group operation, but the subgroup of ''G'' generated by all commutators is closed and is called the ''derived group'' or the ''commutator subgroup'' of ''G''. Commutators are used to define nilpotent and solvable groups and the largest abelian quotient group. The definition of the commutator above is used throughout this article, but many other group theorists define the commutator as :. Identities (group theory) Commutator identities are an important tool in group theory. The expr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lorentz Transformation
In physics, the Lorentz transformations are a six-parameter family of linear transformations from a coordinate frame in spacetime to another frame that moves at a constant velocity relative to the former. The respective inverse transformation is then parameterized by the negative of this velocity. The transformations are named after the Dutch physicist Hendrik Lorentz. The most common form of the transformation, parametrized by the real constant v, representing a velocity confined to the -direction, is expressed as \begin t' &= \gamma \left( t - \frac \right) \\ x' &= \gamma \left( x - v t \right)\\ y' &= y \\ z' &= z \end where and are the coordinates of an event in two frames with the origins coinciding at 0, where the primed frame is seen from the unprimed frame as moving with speed along the -axis, where is the speed of light, and \gamma = \left ( \sqrt\right )^ is the Lorentz factor. When speed is much smaller than , the Lorentz factor is negligibly different from 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relativistic Mechanics
In physics, relativistic mechanics refers to mechanics compatible with special relativity (SR) and general relativity (GR). It provides a non-quantum mechanical description of a system of particles, or of a fluid, in cases where the velocities of moving objects are comparable to the speed of light ''c''. As a result, classical mechanics is extended correctly to particles traveling at high velocities and energies, and provides a consistent inclusion of electromagnetism with the mechanics of particles. This was not possible in Galilean relativity, where it would be permitted for particles and light to travel at ''any'' speed, including faster than light. The foundations of relativistic mechanics are the postulates of special relativity and general relativity. The unification of SR with quantum mechanics is relativistic quantum mechanics, while attempts for that of GR is quantum gravity, an unsolved problem in physics. As with classical mechanics, the subject can be divided into "kin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ole Rømer
Ole Christensen Rømer (; 25 September 1644 – 19 September 1710) was a Danish astronomer who, in 1676, made the first measurement of the speed of light. Rømer also invented the modern thermometer showing the temperature between two fixed points, namely the points at which water respectively boils and freezes. In scientific literature, alternative spellings such as "Roemer", "Römer", or "Romer" are common. Biography Rømer was born on 25 September 1644 in Århus to merchant and skipper Christen Pedersen (died 1663), and Anna Olufsdatter Storm ( – 1690), daughter of a well-to-do alderman. Since 1642, Christen Pedersen had taken to using the name Rømer, which means that he was from the Danish island of Rømø, to distinguish himself from a couple of other people named Christen Pedersen. There are few records of Ole Rømer before 1662, when he graduated from the old Aarhus Katedralskole (the Cathedral school of Aarhus), moved to Copenhagen and matriculated at the U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soviet Physics Uspekhi
''Physics-Uspekhi'' is a peer-reviewed scientific journal. It is an English translation of the Russian journal of physics, ''Uspekhi Fizicheskikh Nauk'' (russian: Успехи физических наук, ''Advances in Physical Sciences'') which was established in 1918. The journal publishes long review papers which are intended to generalize and summarize previously published results, making them easier to use and to understand. The journal covers all topics of modern physics. The English version has existed since 1958, first under the name ''Soviet Physics Uspekhi'' and after 1993 as ''Physics-Uspekhi''. The year 2008 marked the 90th birthday with a jubilee retrospective. The founder of the journal, Eduard Shpolsky, was editor-in-chief from 1918 to his death in 1975. Vitaly Ginzburg, connected with the journal since before World War II, was appointed editor-in-chief in 1998. In his 2006 Nobel autobiography, Ginzburg called it "a good and useful journal" and credited its "mainte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pedagogical Patterns
A pedagogical pattern is the re-usable form of a solution to a problem or task in pedagogy, analogous to how a design pattern is the re-usable form of a solution to a design problem. Pedagogical patterns are used to document and share best practices of teaching. A network of interrelated pedagogical patterns is an example of a pattern language. Overview In a 2001 paper for SIGCSE, Joseph Bergin wrote: Example structure of a pattern Mitchell Weisburgh proposed nine aspects to documenting a pedagogical pattern for a certain skill. Not every pattern needs to include all nine. His listing is reproduced below: * ''Name'' – single word or short phrase that refers to the pattern. This allows for rapid association and retrieval. * ''Problem'' – definition of a problem, including its intent or a desired outcome, and symptoms that would indicate that this problem exists. * ''Context'' – preconditions which must exist in order for that problem to occur; this is often a situation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of High Energy Physics
The ''Journal of High Energy Physics'' is a monthly peer-reviewed open access scientific journal covering the field of high energy physics. It is published by Springer Science+Business Media on behalf of the International School for Advanced Studies. The journal is part of the SCOAP3 initiative. According to the ''Journal Citation Reports'', the journal has a 2020 impact factor of 5.810. References External links *Journal pageat International School for Advanced Studies The International School for Advanced Studies (Italian: ''Scuola Internazionale Superiore di Studi Avanzati''; SISSA) is an international, state-supported, post-graduate-education and research institute in Trieste, Italy. SISSA is active in th ... website English-language journals Monthly journals Physics journals Publications established in 1997 Springer Science+Business Media academic journals Academic journals associated with learned and professional societies Particle physics journals {{p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black-hole Thermodynamics
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, where by the same year, he proposed no-hair theorems. In 1973 Bekenstein suggested \frac\appr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hawking Radiation
Hawking radiation is theoretical black body radiation that is theorized to be released outside a black hole's event horizon because of relativistic quantum effects. It is named after the physicist Stephen Hawking, who developed a theoretical argument for its existence in 1974. Hawking radiation is a purely kinematic effect that is generic to Lorentzian geometries containing event horizons or local apparent horizons. Hawking radiation reduces the mass and rotational energy of black holes and is therefore also theorized to cause black hole evaporation. Because of this, black holes that do not gain mass through other means are expected to shrink and ultimately vanish. For all except the smallest black holes, this would happen extremely slowly. The radiation temperature is inversely proportional to the black hole's mass, so micro black holes are predicted to be larger emitters of radiation than larger black holes and should dissipate faster. Overview Black holes are astrophysica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
