{{Short description|Operator characterizing the phase of a system}} {{more citations needed|date=August 2014}} In quantum field theory, an '''order operator''' or an '''order field''' is a quantum field version of Landau's order parameter whose expectation value characterizes phase transitions. There exists a dual version of it, the disorder operator or disorder field, whose expectation value characterizes a phase transition by indicating the prolific presence of defect or vortex lines in an ordered phase.
The '''disorder operator''' is an operator that creates a discontinuity of the ordinary order operators or a monodromy for their values. For example, a 't Hooft operator is a disorder operator. So is the Jordan–Wigner transformation. The concept of a disorder observable was first introduced in the context of 2D Ising spin lattices, where a phase transition between spin-aligned (magnetized) and disordered phases happens at some temperature.<ref>Fradkin, E. J Stat Phys (2017) 167: 427. https://doi.org/10.1007/s10955-017-1737-7</ref>
==See also== * Operator (physics)
==Books== * Kleinert, Hagen, ''Gauge Fields in Condensed Matter'', Vol. I, " SUPERFLOW AND VORTEX LINES", pp. 1–742, Vol. II, "STRESSES AND DEFECTS", pp. 743–1456, [https://archive.today/20060514143926/http://www.worldscibooks.com/physics/0356.htm World Scientific (Singapore, 1989)]; Paperback {{ISBN|9971-5-0210-0}} '' (also available online: [http://www.physik.fu-berlin.de/~kleinert/kleiner_reb1/contents1.html Vol. I] {{Webarchive|url=https://web.archive.org/web/20080527174206/http://www.physik.fu-berlin.de/~kleinert/kleiner_reb1/contents1.html |date=2008-05-27 }} and [http://www.physik.fu-berlin.de/~kleinert/kleiner_reb1/contents2.html Vol. II] {{Webarchive|url=https://web.archive.org/web/20080527174211/http://www.physik.fu-berlin.de/~kleinert/kleiner_reb1/contents2.html |date=2008-05-27 }})''
==References== {{Reflist}}
Category:Quantum field theory Category:Statistical mechanics Category:Phase transitions
{{quantum-stub}}