Symmetry 2010, 2(3), 1401-1422; doi:10.3390/sym2031401
Article

Symmetry, Symmetry Breaking and Topology

Received: 1 February 2010; in revised form: 30 April 2010 / Accepted: 5 July 2010 / Published: 7 July 2010
(This article belongs to the Special Issue Symmetry Breaking Phenomena)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The ground state of a system with symmetry can be described by a group G. This symmetry group G can be discrete or continuous. Thus for a crystal G is a finite group while for the vacuum state of a grand unified theory G is a continuous Lie group. The ground state symmetry described by G can change spontaneously from G to one of its subgroups H as the external parameters of the system are modified. Such a macroscopic change of the ground state symmetry of a system from G to H correspond to a “phase transition”. Such phase transitions have been extensively studied within a framework due to Landau. A vast range of systems can be described using Landau’s approach, however there are also systems where the framework does not work. Recently there has been growing interest in looking at such non-Landau type of phase transitions. For instance there are several “quantum phase transitions” that are not of the Landau type. In this short review we first describe a refined version of Landau’s approach in which topological ideas are used together with group theory. The combined use of group theory and topological arguments allows us to determine selection rule which forbid transitions from G to certain of its subgroups. We end by making a few brief remarks about non-Landau type of phase transition.
Keywords: symmetry breaking; group theory; topology
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MDPI and ACS Style

Sen, S. Symmetry, Symmetry Breaking and Topology. Symmetry 2010, 2, 1401-1422.

AMA Style

Sen S. Symmetry, Symmetry Breaking and Topology. Symmetry. 2010; 2(3):1401-1422.

Chicago/Turabian Style

Sen, Siddhartha. 2010. "Symmetry, Symmetry Breaking and Topology." Symmetry 2, no. 3: 1401-1422.

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