supersymmetry


supersymmetry
/sooh"peuhr sim"i tree/, n. Physics.
a hypothetical symmetry among groups of particles containing fermions and bosons, esp. in theories of gravity (supergravity) that unify electromagnetism, the weak force, and the strong force with gravity into a single unified force.
[1970-75; SUPER- + SYMMETRY]

* * *

      in particle physics (physics), a symmetry between fermions (fermion) (subatomic particles with half-integer values of intrinsic angular momentum, or spin) and bosons (boson) (particles with integer values of spin). Supersymmetry is a complex mathematical framework based on the theory of group transformations that was developed beginning in the early 1970s to understand at a more-fundamental level the burgeoning number of subatomic particles (subatomic particle) being produced in high-energy particle accelerator experiments. It has evolved to address internal inconsistencies that arose in attempts to unify the forces in the standard model of particle physics. Supersymmetry is an essential feature of supergravity, the quantum field theory of the gravitational force (gravitation), and of string theory, an ambitious attempt to provide a self-consistent quantum theory unifying all particles and forces in nature.

      A physical entity is said to exhibit symmetry when it appears unchanged after undergoing a transformation operation. A square, for example, has a fourfold symmetry by which it appears the same when rotated about its centre through 90, 180, 270, and 360 degrees; four 90-degree rotations bring the square back to its original position. Symmetry with respect to time and space transformations is embodied within physical laws such as the conservation of energy (energy, conservation of) and the conservation of momentum (momentum, conservation of). With supersymmetry, fermions can be transformed into bosons without changing the structure of the underlying theory of the particles and their interactions. Thus, supersymmetry provides a relationship between the elementary particles that make up matter—quarks (quark) and leptons (lepton), which are all fermions—and the “force-carrier” particles that transmit the fundamental interactions (fundamental interaction) of matter (all bosons). By showing that one type of particle is in effect a different facet of the other type, supersymmetry reduces the number of basic types of particle from two to one.

      When a fermion is transformed into a boson and then back again into a fermion, it turns out that the particle has moved in space, an effect that is related to special relativity (relativity). Supersymmetry therefore relates transformations in an internal property of particles (spin) to transformations in space-time. In particular, when supersymmetry is made a “local” symmetry, so that the transformations vary over space-time, it automatically includes a particle with a spin of 2, which can be identified as the graviton, the “force carrier” associated with gravity. Theories involving supersymmetry in its local form are therefore often known as supergravity theories.

      Supersymmetry also plays an important role in modern theories of particle physics because the new particles that it requires can eliminate various infinite quantities that otherwise appear in calculations of particle interactions at high energies, particularly in attempts at unified theories of the fundamental forces. These new particles are the bosons (or fermions) into which the known fermions (or bosons) are transformed by supersymmetry. Thus, supersymmetry implies a doubling of the number of the known particles. For example, fermions such as electrons and quarks should have bosonic supersymmetric partners, which have been given the names of selectrons and squarks. Similarly, known bosons such as the photon and the gluon should have fermionic supersymmetric partners, called the photino and the gluino. There has been no experimental evidence that such “superparticles” exist. If they do indeed exist, their masses could be in the range of 50 to 1,000 times that of the proton.

Christine Sutton
 

* * *


Universalium. 2010.

Look at other dictionaries:

  • supersymmetry — [so͞o΄pər sim′ə trē] n. Nuclear Physics any of various mathematical theories that attempt to unify all the forces and subatomic particles of nature supersymmetric [so͞o΄pərsi me′trik] adj …   English World dictionary

  • Supersymmetry — In particle physics, supersymmetry (often abbreviated SUSY) is a symmetry that relates elementary particles of one spin to another particle that differs by half a unit of spin and are known as superpartners. In other words, in a supersymmetric… …   Wikipedia

  • supersymmetry — supersimetrija statusas T sritis fizika atitikmenys: angl. supersymmetry vok. Supersymmetrie, f rus. суперсимметрия, f pranc. supersymétrie, f …   Fizikos terminų žodynas

  • supersymmetry — noun (physics) a theory that tries to link the four fundamental forces according to supersymmetry each force emerged separately during the big bang • Topics: ↑physics, ↑natural philosophy • Hypernyms: ↑scientific theory …   Useful english dictionary

  • supersymmetry — noun Date: 1974 the correspondence between fermions and bosons of identical mass that is postulated to have existed during the opening moments of the big bang and that relates gravity to the other forces of nature • supersymmetric adjective …   New Collegiate Dictionary

  • supersymmetry — noun A theory that attempts to unify the fundamental physical forces and which proposes a physical symmetry between bosons and fermions Syn: SUSY …   Wiktionary

  • supersymmetry — noun Physics a very general type of mathematical symmetry which relates fermions and bosons. Derivatives supersymmetric adjective …   English new terms dictionary

  • supersymmetry — su·per·symmetry …   English syllables

  • supersymmetry — su•per•sym•me•try [[t]ˌsu pərˈsɪm ɪ tri[/t]] n. phs an abstract symmetry relating fermions and bosons, used as the basis for most quantum theories of gravitation • Etymology: 1970–75 su per•sym•met′ric sɪˈmɛ trɪk adj …   From formal English to slang

  • supersymmetry — /supəˈsɪmətri/ (say soohpuh simuhtree) noun a postulated symmetrical relationship between elementary particles which connects fermions and bosons …   Australian English dictionary


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.