Gauge boson. The Standard Model of elementary particles, with the gauge bosons in the fourth column in red In particle physics, a gauge boson is a force carrier, a bosonic particle that carries any of the fundamental interactions of nature.[1][2] Elementary particles, whose interactions are described by a gauge theory, interact with each other by the exchange of gauge bosons—usually as virtual particles. Gauge bosons in the Standard Model[edit] The Standard Model of particle physics recognizes three kinds of gauge bosons: photons, which carry the electromagnetic interaction; W and Z bosons, which carry the weak interaction; and gluons, which carry the strong interaction.[3] Isolated gluons do not occur at low energies because they are color-charged, and subject to color confinement. Multiplicity of gauge bosons[edit] Massive gauge bosons[edit] According to the Standard Model, the W and Z bosons gain mass via the Higgs mechanism. Beyond the Standard Model[edit] Grand unification theories[edit] See also[edit]
Gauge theory. Kaluza–Klein theory. This article is about gravitation and electromagnetism. For the mathematical generalization of K theory, see KK-theory. In 1926, Oskar Klein gave Kaluza's classical 5-dimensional theory a quantum interpretation,[3][4] to accord with the then-recent discoveries of Heisenberg and Schroedinger. Klein introduced the hypothesis that the fifth dimension was curled up and microscopic, to explain the cylinder condition. Klein also calculated a scale for the fifth dimension based on the quantum of charge.
It wasn't until the 1940s that the classical theory was completed, and the full field equations including the scalar field were obtained by three independent research groups:[5] Thiry,[6][7][8] working in France on his dissertation under Lichnerowicz; Jordan, Ludwig, and Müller in Germany,[9][10][11][12][13] with critical input from Pauli and Fierz; and Scherrer [14][15][16] working alone in Switzerland. The Kaluza Hypothesis[edit] , where roman indices span 5 dimensions. . Where the index where or. Visuals: Quark Flux Tubes. Gluon field strength tensor. In theoretical particle physics, the gluon field strength tensor is a second order tensor field characterizing the gluon interaction between quarks. The strong interaction is one of the fundamental interactions of nature, and the quantum field theory (QFT) to describe it is called quantum chromodynamics (QCD).
Quarks interact with each other by the strong force due to their color charge, mediated by gluons. Gluons themselves possess color charge and can mutually interact. The gluon field strength tensor is a rank 2 tensor field on the spacetime with values in the adjoint bundle of the chromodynamical SU(3) gauge group (see vector bundle for necessary definitions). Throughout, Latin indices (typically a, b, c, n) take values 1, 2, ..., 8 for the eight gluon color charges, while Greek indices (typically α, β, μ, ν) take values 0 for timelike components and 1, 2, 3 for spacelike components of four-vectors and four-dimensional spacetime tensors. Definition[edit] Tensor components[edit] where: Quantum chromodynamics. In theoretical physics, quantum chromodynamics (QCD) is a theory of strong interactions, a fundamental force describing the interactions between quarks and gluons which make up hadrons such as the proton, neutron and pion.
QCD is a type of quantum field theory called a non-abelian gauge theory with symmetry group SU(3). The QCD analog of electric charge is a property called 'color'. Gluons are the force carrier of the theory, like photons are for the electromagnetic force quantum electrodynamics. The theory is an important part of the Standard Model of particle physics. QCD enjoys two peculiar properties: Confinement, which means that the force between quarks does not diminish as they are separated.
There is no known phase-transition line separating these two properties; confinement is dominant in low-energy scales but, as energy increases, asymptotic freedom becomes dominant. Terminology[edit] History[edit] Three identical quarks cannot form an antisymmetric S-state. Theory[edit] Weak hypercharge. Definition[edit] It is the generator of the U(1) component of the electroweak gauge group, SU(2)×U(1) and its associated quantum field B mixes with the W3 electroweak quantum field to produce the observed Z gauge boson and the photon of quantum electrodynamics.
Weak hypercharge, usually written as YW, satisfies the equality: where Q is the electrical charge (in elementary charge units) and T3 is the third component of weak isospin. Rearranging, the weak hypercharge can be explicitly defined as: Note: sometimes weak hypercharge is scaled so that although this is a minority usage.[2] Baryon and lepton number[edit] Weak hypercharge is related to baryon number minus lepton number via: Neutron decay[edit] n → p + e− + ν e Hence neutron decay conserves baryon number B and lepton number L separately, so also the difference B − L is conserved. Proton decay[edit] Proton decay is a prediction of many grand unification theories. p+ → e+ + π0 → e+ + 2γ See also[edit] Notes[edit] Jump up ^ J. Gauge boson. Higgs mechanism. In particle physics, the Higgs mechanism is essential to explain the generation mechanism of the property "mass" for gauge bosons. In the Standard Model, the three weak bosons gain mass through the Higgs mechanism by interacting with the Higgs field that permeates all space.
Normally bosons are massless, but the W+, W-, and Z bosons have values around 80 GeV/c2. In gauge theory, the Higgs field induces a spontaneous symmetry breaking, where instead of the usual transverse Nambu–Goldstone boson, the longitudinal Higgs boson appears. The simplest implementation of the mechanism adds an extra Higgs field to the gauge theory. The specific spontaneous symmetry breaking of the underlying local symmetry, which is similar to that one appearing in the theory of superconductivity, triggers conversion of the longitudinal field component to the Higgs boson, which interacts with itself and (at least a part of) the other fields in the theory, so as to produce mass terms for the three gauge bosons.
Bose–Einstein condensate. A Bose–Einstein condensate (BEC) is a state of matter of a dilute gas of bosons cooled to temperatures very close to absolute zero (that is, very near 0 K or −273.15 °C[1]). Under such conditions, a large fraction of the bosons occupy the lowest quantum state, at which point quantum effects become apparent on a macroscopic scale. These effects are called macroscopic quantum phenomena. Although later experiments have revealed complex interactions, this state of matter was first predicted, generally, in 1924–25 by Satyendra Nath Bose and Albert Einstein. History[edit] Velocity-distribution data (3 views) for a gas of rubidium atoms, confirming the discovery of a new phase of matter, the Bose–Einstein condensate. Left: just before the appearance of a Bose–Einstein condensate. In 1938 Fritz London proposed BEC as a mechanism for superfluidity in 4He and superconductivity.[4][5] Concept[edit] where: Einstein's non-interacting model[edit] and .
If we can tell which particle is which, there are or . . G-factor (physics) For the acceleration-related quantity in mechanics, see g-force. A g-factor (also called g value or dimensionless magnetic moment) is a dimensionless quantity which characterizes the magnetic moment and gyromagnetic ratio of a particle or nucleus. It is essentially a proportionality constant that relates the observed magnetic moment μ of a particle to the appropriate angular momentum quantum number and the appropriate fundamental quantum unit of magnetism, usually the Bohr magneton or nuclear magneton. The most famous of these is the electron spin g-factor (more often called simply the electron g-factor), ge, defined by The z-component of the magnetic moment then becomes The value gS is roughly equal to 2.002319, and is known to extraordinary precision.[1][2] The reason it is not precisely two is explained by quantum electrodynamics calculation of the anomalous magnetic dipole moment.[3] Secondly, the electron orbital g-factor, gL, is defined by which, since gL = 1, is just μBml.