the disorder and the thermal average may be treated on the same footing. See also In high energy physics, the formation of the chiral condensate in quantum chromodynamics is an ordering transition; it is discussed in terms of superselection. Entropy Topological order Impurity superstructure (physics) Further reading H Kleinert: Gauge Fields in Condensed Matter (, 2 volumes) Singapore: World Scientific (1989). Statistical mechanics Crystallography