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Gravitino
In supergravity theories combining general relativity and supersymmetry, the gravitino () is the gauge fermion supersymmetric partner of the hypothesized graviton. It has been suggested as a candidate for dark matter. If it exists, it is a fermion of spin and therefore obeys the Rarita–Schwinger equation. The gravitino field is conventionally written as ''ψμα'' with a four-vector index and a spinor index. For one would get negative norm modes, as with every massless particle of spin 1 or higher. These modes are unphysical, and for consistency there must be a gauge symmetry which cancels these modes: , where ''εα''(''x'') is a spinor function of spacetime. This gauge symmetry is a local supersymmetry transformation, and the resulting theory is supergravity. Thus the gravitino is the fermion mediating supergravity interactions, just as the photon is mediating electromagnetism, and the graviton is presumably mediating gravitation. Whenever supersymmetry is br ... [...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] |
Lightest Supersymmetric Particle
In particle physics, the lightest supersymmetric particle (LSP) is the generic name given to the lightest of the additional hypothetical particles found in supersymmetric models. In models with R-parity conservation, the LSP is stable; in other words, it cannot decay into any Standard Model particle, since all SM particles have the opposite R-parity. There is extensive observational evidence for an additional component of the matter density in the universe, which goes under the name dark matter. The LSP of supersymmetric models is a dark matter candidate and is a weakly interacting massive particle (WIMP). Constraints on LSP from cosmology The LSP is unlikely to be a charged wino, charged higgsino, slepton, sneutrino, gluino, squark, or gravitino but is most likely a mixture of neutral higgsinos, the bino and the neutral winos, i.e. a neutralino. In particular, if the LSP were charged (and is abundant in our galaxy) such particles would have been captured by the Earth's mag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graviton
In theories of quantum gravity, the graviton is the hypothetical elementary particle that mediates the force of gravitational interaction. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity. In string theory, believed by some to be a consistent theory of quantum gravity, the graviton is a massless state of a fundamental string. If it exists, the graviton is expected to be massless because the gravitational force has a very long range and appears to propagate at the speed of light. The graviton must be a spin-2 boson because the source of gravitation is the stress–energy tensor, a second-order tensor (compared with electromagnetism's spin-1 photon, the source of which is the four-current, a first-order tensor). Additionally, it can be shown that any massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field would couple to the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elementary Particle
In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a consequence of flavor and color combinations and antimatter, the fermions and bosons are known to have 48 and 13 variations, respectively. Among the 61 elementary particles embraced by the Standard Model number: electrons and other leptons, quarks, and the fundamental bosons. Subatomic particles such as protons or neutrons, which contain two or more elementary particles, are known as composite particles. Ordinary matter is composed of atoms, themselves once thought to be indivisible elementary particles. The name ''atom'' comes from the Ancient Greek word ''ἄτομος'' ( atomos) which means ''indivisible'' or ''uncuttable''. Despite the theories about atoms that had existed for thousands of years, the factual existence of ato ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitation
In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force between objects and the Earth. This force is dominated by the combined gravitational interactions of particles but also includes effect of the Earth's rotation. Gravity gives weight to physical objects and is essential to understanding the mechanisms responsible for surface water waves and lunar tides. Gravity also has many important biological functions, helping to guide the growth of plants through the process of gravitropism and influencing the circulation of fluids in multicellular organisms. The gravitational attraction between primordial hydrogen and clumps of dark matter in the early universe caused the hydrogen gas to coalesce, eventually condensing and fusing to form stars. At larger scales this results in galaxies and clusters ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R-parity
R-parity is a concept in particle physics. In the Minimal Supersymmetric Standard Model, baryon number and lepton number are no longer conserved by all of the renormalizable couplings in the theory. Since baryon number and lepton number conservation have been tested very precisely, these couplings need to be very small in order not to be in conflict with experimental data. R-parity is a \mathbb_2 symmetry acting on the Minimal Supersymmetric Standard Model (MSSM) fields that forbids these couplings and can be defined as :P_\mathrm = (-1)^, or, equivalently, as :P_\mathrm = (-1)^, where is spin, is baryon number, and is lepton number. All Standard Model particles have R-parity of +1 while supersymmetric particles have R-parity of −1. Note that there are different forms of parity with different effects and principles, one should not confuse this parity with any other parity. Dark matter candidate With R-parity being preserved, the lightest supersymmetric particle ( LSP) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambda-CDM Model
The Lambda-CDM, Lambda cold dark matter, or ΛCDM model is a mathematical model of the Big Bang theory with three major components: # a cosmological constant, denoted by lambda (Λ), associated with dark energy; # the postulated cold dark matter, denoted by CDM; # ordinary matter. It is the current ''standard model'' of Big Bang cosmology, as it is the simplest model that provides a reasonably good account of: * the existence and structure of the cosmic microwave background; * the large-scale structure in the distribution of galaxies; * the observed abundances of hydrogen (including deuterium), helium, and lithium; * the accelerating expansion of the universe observed in the light from distant galaxies and supernovae. The model assumes that general relativity is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a concordance cosmology, after a period when disparate observed properties of the universe appeared mutually inconsistent, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Felix Pirani
__NOTOC__ Felix Arnold Edward Pirani (2 February 1928 – 31 December 2015) was a British theoretical physicist, and professor at King's College London, specialising in gravitational physics and general relativity. Pirani and Hermann Bondi wrote a series of articles (1959 to 1989) that established the existence of plane wave solutions for gravitational waves based on general relativity. During the last half of the 20th century Pirani was politically active, studied disarmament and advocated the responsible use of science. His most famous scientific results include works on the physical meaning of the curvature tensor, gravitational waves, and the algebraic classification of the Weyl tensor, which he discovered in 1957 independently of A.Z. Petrov and is sometimes called the Petrov–Pirani classification. Early life and education Pirani was born in England, to parents who were both musicians. Pirani's family, who were Jewish, moved to Canada at the start of World War II ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heinz Pagels
Heinz Rudolf Pagels (February 19, 1939 – July 23, 1988) was an American physicist, an associate professor of physics at Rockefeller University, the executive director and chief executive officer of the New York Academy of Sciences, and president of the International League for Human Rights. He wrote the popular science books ''The Cosmic Code'' (1982), '' Perfect Symmetry'' (1985), and '' The Dreams of Reason: The Computer and the Rise of the Sciences of Complexity'' (1988). Early life Pagels was a 1956 graduate of Woodberry Forest School in Virginia. The school awards The Heinz R. Pagels Jr. Physics Memorial Award each year to a graduating student who has demonstrated outstanding achievement in physics. Career Pagels obtained his PhD in elementary particle physics from Stanford University under the guidance of Sidney Drell. His technical work included the ''Physics Reports'' review articles ''Quantum Chromodynamics'' (with W.Marciano) and "Departures from Chiral Symmetry". A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sidney Coleman
Sidney Richard Coleman (7 March 1937 – 18 November 2007) was an American theoretical physicist noted for his research in high-energy physics. Life and work Sidney Coleman grew up on the Far North Side of Chicago. In 1957, he received his undergraduate degree from the Illinois Institute of Technology physics department. Coleman received his Ph.D. from the California Institute of Technology in 1962, where he was advised by Murray Gell-Mann. He moved to Harvard University that year, where he spent his entire career, meeting his wife Diana there in the late 1970s. They were married in 1982. "He was a giant in a peculiar sense, because he's not known to the general populace," Nobel laureate Sheldon Glashow told the Boston Globe. "He's not a Stephen Hawking; he has virtually no visibility outside. But within the community of theoretical physicists, he's kind of a major god. He is the physicist's physicist." In 1966, Antonino Zichichi recruited Coleman as a lecturer at the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Review
''Physical Review'' is a peer-reviewed scientific journal. The journal was established in 1893 by Edward Nichols. It publishes original research as well as scientific and literature reviews on all aspects of physics. It is published by the American Physical Society (APS). The journal is in its third series, and is split in several sub-journals each covering a particular field of physics. It has a sister journal, '' Physical Review Letters'', which publishes shorter articles of broader interest. History ''Physical Review'' commenced publication in July 1893, organized by Cornell University professor Edward Nichols and helped by the new president of Cornell, J. Gould Schurman. The journal was managed and edited at Cornell in upstate New York from 1893 to 1913 by Nichols, Ernest Merritt, and Frederick Bedell. The 33 volumes published during this time constitute ''Physical Review Series I''. The American Physical Society (APS), founded in 1899, took over its publicati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peter Van Nieuwenhuizen
Peter van Nieuwenhuizen (; born October 26, 1938) is a Dutch theoretical physicist. He is a distinguished Professor at Stony Brook University in the United States. Widely known for his contributions to String theory, Supersymmetry, Supergravity and Field theory. He is best known for his discovery of supergravity with Sergio Ferrara and Daniel Z. Freedman for which he along with his collaborators won the Breakthrough Prize in Fundamental Physics in 2019. Life and career Peter van Nieuwenhuizen studied physics and mathematics at the University of Utrecht, where he obtained in 1971 his Ph.D. under the supervision of later Nobel laureate Martinus Veltman. After his studies in Utrecht he went to CERN (Geneva), the University of Paris in Orsay, and Brandeis University (Waltham). In 1975 he joined the Institute for Theoretical Physics, now named C. N. Yang Institute for Theoretical Physics, of the Stony Brook University, where he succeeded Nobel laureate C. N. Yang as its di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
