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unified theory
subject			fact

unified theory	has definition In particle physics, any theory exposing relationships between seemingly disparate classes of particles. More generally, a theory that gathers a wide range of fundamentally different phenomena under a single precept, as in Maxwell's discovery that light and magnetism are aspects of a single, electromagnetic force.
	has definition Any theory that describes all four forces and all of matter within a single, all-encompassing framework.
	is a kind of theory
theory	has validity correct or incorrect with caveats
	has author or reasearch group
	has domain a field of research
	has date or a range of dates for which the theory was active

Kinds of unified theory :

• Gauge theory (8 facts) (Yang-Mills theories) - A theory whose dynamics originate from a symmetry. That is, the formulae describing the theory (in particular, the Lagrangian) are unchanged under certain symmetry transformations, called "gauge" transformations. For example, the equations of classical electrodynamics are invariant under local redefinitions of the electrostatic potential. This symmetry is ultimately responsible for the conservation of electric charge. However, in quantum electrodynamics this gauge symmetry is reinterpreted as invariance under local redefinitions of the phase of the electron wave function., Account of forces that views them as arising from broken symmetries., A theory that treats force in a geometrical way in terms of global and local symmetries., In 1973 David Gross, Frank Wilczek, and David Politzer showed that these theories possess a property called asymptotic freedom, just what was needed for a theory of how quarks bind to form protons and neutrons. The new theory, dubbed quantum chromodynamics or QCD, proposed that the color of the quarks acts as the charge of the Yang-Mills interactions.
• grand unified theory (8 facts) (grand unification, GUT) - Class of theories that purport to reveal identities linking the strong and electroweak forces. The differences between these forces in nature today is attributed to the breaking of symmetrical relationships among force-carrying particles as the very early universe expanded and cooled., A speculative class of theories of particle interactions, first developed in 1974, which attempt to describe electromagnetism, the weak interactions, and the strong interactions in a fully unified theory. Of the known forces, only gravitation is omitted., Theory in physics that attempt to explain the forces of nature as manifestations of a single underlying force., An attempt to produce a unification of all the forces of nature. While some success was made in unifying the gluon force between quarks with the electroweak force, problems always arose when gravity was included. Grand unification eventually gave way to superstring theory., Class of theories that merge all three nongravitational forces into a single theoretical framework.
• Kaluza-Klein theory (4 facts) - Class of theories incorporating extra curled-up dimensions, together with quantum mechanics., An early attempt to unify general relativity and electromagnetism by working in five dimensions. The electromagnetic field was obtained by curling up or compactifying the extra dimension. With the advent of higher dimensional theories such as superstrings, the Kaluza-Klein approach came back into fashion.
• quantum gravity (4 facts) - A theory of gravity that would properly include quantum mechanics. To date, there is no complete and self-consistent theory of quantum gravity, although successful quantum theories have been found for all the forces of nature except gravity. (See quantum mechanics.), A general term used to describe attempts to quantize gravity. The elementary particle of the gravitational field is the graviton., A theory that successfully mergers quantum mechanics and general relativity, possibly involving modifications of one or both. String theory is an example of a theory of quantum gravity.
• string theory (12 kinds, 35 facts) - Fundamental one-dimensional object that is the essential ingredient in string theory., Nambu's original idea that the elementary particles could be described as extended, one-dimensional objects was called string theory. Since the ends of Nambu's strings whipped around at the speed of light they were also called light strings. Later attempts to include the spin half fermions within a string theory led to the term spinning strings. Strings that possess supersymmetry are called superstrings. Heterotic strings combine spaces of two different dimensionalities. The term string is used in a generic way to describe all these different variations, including superstrings., The hypothesized, basic constituents of matter, according to new theories of physics. In earlier theories of physics, the basic constituents of matter were point-like particles, such as electrons, which interacted with other particles at a point. According to the string theory, the basic constituents are 1-dimensional structures called strings. There are completely different strings, called cosmic strings, which can form according to some theories and which may extend for great distances in space. Postulated to have formed as a result of processes in the early universe, cosmic strings are 1-dimensional structures of enormous energy, extending for perhaps thousands or millions of light years in space. There is no good observational evidence that either kind of strings exist. (See superstring theory.), A theory in which the fundamental constituents of matter are not particles but tiny one-dimensional objects, which we can think of as strings. These strings are so minute (only 10^-33 cm long) that, even at current experimental energies, they seem to behave just like particles. So, according to string theory, what we call "elementary particles" are actually tiny strings. each of which is vibrating in a way characteristic of the particular "elementary particle"., Unified theory of the universe postulating that fundamental ingredients of nature are not zero-dimensional point particles but tiny one-dimensional filaments called strings. String theory harmoniously unites quantum mechanics and general relativity the previously known laws of the small and the large, that are otherwise incompatible. Often short for superstring theory., Theory that subatomic particles actually have extension along one axis, and that their properties are determined by the arrangement and vibration of the strings.
• supersymmetry (5 kinds, 17 facts) - A symmetry relating fermions and bosons. If supersymmetry is a true symmetry of nature, then every "ordinary" particle has a corresponding "superpartner" which differs in spin by half a unit., A symmetry principle that relates the properties of particles with a whole number amount of spin (bosons) to those with half a whole (odd) number amount of spin (fermions)., A symmetry that relates the fermions (fractional spin particles) to the bosons (elementary particles with integral spin)., Class of theories that seek to identify symmetrical relationships linking fermions and bosons - i.e., particles of half integer spin, like electrons, protoins, and neutrinos, with those of integral spin, like photons and gluons. If attainable, a fully realized supersymmetry theory would provide a unified account of all four fundamental forces, and might well shed light on the very early evolution of the universe as well., A mathematical property of some theories of physics proposing that every particle of integer spin (intrinsic angular momentum) has a partner of half integer spin. For example, the photon, which is the particle of light, has a spin of 1 unit. Its hypothesized super symmetric partner is called the photino, which would have a spin of 1/2 units.
• superunified theory (3 facts) - While grand unified theories attempt to describe three of the four known interactions of nature - the weak, strong, and electromagnetic interactions - in a unified way, the fourth interaction, gravity, is omitted. Theories which attempt to include gravity as well, such as superstrings, are called superunified., Hypothetical theory that presumably would show how all four fundamental forces of nature functioned as a single force in the extremely early universe. The best current candidates for such a potential achievement are thought to be supersymmetry and string theory.
• theory of everything (3 facts) (TOE) - Theory of Everything. A quantum-mechanical theory that encompasses all forces and all matter.