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symmetry
subject			fact

symmetry	has antonym symmetry breaking
	has definition A property of a physical system that does not change when the system is transformed in some manner. For instance, a sphere is rotationally symmetrical since its appearance does not change if it is rotated.
	has definition State of a system such that it has a significant quantity that remains invariant after a transformation. More generally, an apt or pleasing proportion based upon such a state.
	has definition The property of being unchanged after some transformation. A square, for example, has a 4-sided rotational symmetry. It appears the same after it is rotated by 90 degrees.
	is a kind of mathematical concept

Kinds of symmetry :

• CPT invariance (3 facts) - A symmetry which is believed to hold true for all particles throughout the course of universal history. It states that matter and antimatter would only react in the same way if the spins of the antimatter particles were reversed and the reaction was caused to run backwards in time., A theory has "CPT invariance" if for every possible reaction between subatomic particles, a reaction can also occur in which the electrical charges of the particles changed to their opposites, the mirror image of the particle trajectories is used, and the directions of motion are reversed. Assuming general notions of modern physics, all conceivable theories of nature are CPT invariant.
• elementary particle symmetry (5 kinds, 15 facts) - Abstract mathematical relationships that relate elementary particles together and allow them to be grouped into families. A particular symmetry transformation has the effect of, in a theoretical way, transforming one elementary particle into another.
• gauge symmetry (3 kinds, 9 facts) - A property of modern theories of physics, formulated in the 1960s and confirmed by experiment. A symmetry, in general, is a property that allows a system to behave in the same way even though it has undergone some change. For instance, a snowflake has a 6-sided "rotational symmetry" - a snowflake appears identical after every 60 degree rotation. A gauge symmetry is something like a rotation, in which the amount of rotation can vary randomly from one point of space to the next. (See field theory.), Symmetry principle underlying the quantum-mechanical description of the three nongravitational forces; the symmetry involves the invariance of a physical system under various shifts in the values of force charges, shifts that can change from place to place and from moment to moment.
• internal symmetry (2 facts) - The properties of different elementary particles can be related to each other by mathematical transformations that look very much like the more familiar symmetry properties of our own physical space. Physicists have therefore hypothesized an abstract internal space in which these internal symmetries are defined. With the help of these internal symmetries, the elementary particles can be gathered into families. The relationship between space-time and these internal symmetries remains to be fully explained.
• isotropy (9 facts) (rotational invariance) - The property of being unchanged by a rotation. A sphere is rotationally invariant, but a rectangle is not. As far as we know the fundamental laws of physics are rotationally invariant., Quality of being the same in all directions., In cosmology, the property that the universe appears the same in all directions. The uniformity of the cosmic background radiation, coming from all directions of space, suggests that on the large scale the universe is isotropic about our position. If we then assume that our position is not unique, we conclude that: the universe appears isotropic about all points. This last result requires that the universe be homogeneous. (See cosmic background radiation; homogeneity.), The same in all directions., Having equal and uniform properties at all points and in all directions. In astronomy the term describes microwave background radiation., A universe is said to be isotropic, from the point of view of a given observer, if it looks the same in all directions. The isotropy of the real universe is seen most strikingly in the cosmic background radiation, which has the same temperature in all directions to an accuracy of about one part in 100,000. See also homogeneous.
• parity (3 facts) - The principle of space-inversion invariance; i.e., no experiment can differentiate between the behavior of a system and that of its mirror image. Parity is conserved in strong interactions, but not in weak ones., The operation which reverses the signs of the coordinate axes used to describe a system, i.e. (x, y, z) -> (-x, -y, -z).