Editing Landau theory (section)

{{Short description|Theory of continuous phase transitions}}
{{confused|Ginzburg–Landau theory}}

'''Landau theory''' (also known as '''Ginzburg–Landau theory''', despite the confusing name<ref>{{Cite journal |last1=Hohenberg |first1=P. C. |last2=Krekhov |first2=A. P. |date=2015-04-04 |title=An introduction to the Ginzburg–Landau theory of phase transitions and nonequilibrium patterns |url=https://www.sciencedirect.com/science/article/pii/S0370157315000514 |journal=Physics Reports |volume=572 |pages=1–42 |doi=10.1016/j.physrep.2015.01.001 |issn=0370-1573|arxiv=1410.7285 |bibcode=2015PhR...572....1H }}</ref>) in [[physics]] is a theory that [[Lev Landau]] introduced in an attempt to formulate a general theory of continuous (i.e., second-order) [[phase transition]]s.<ref>{{cite journal|title=On the Theory of Phase Transitions|url=http://www.ujp.bitp.kiev.ua/files/journals/53/si/53SI08p.pdf|author=Lev D. Landau|journal=Zh. Eksp. Teor. Fiz.|volume=7|page=19-32|year=1937|archive-url=https://web.archive.org/web/20151214124950/http://www.ujp.bitp.kiev.ua/files/journals/53/si/53SI08p.pdf|archive-date=Dec 14, 2015}}</ref> It can also be adapted to systems under externally-applied fields, and used as a quantitative model for discontinuous (i.e., first-order) transitions. Although the theory has now been superseded by the [[renormalization group]] and scaling theory formulations, it remains an exceptionally broad and powerful framework for phase transitions, and the associated concept of the [[Phase transitions#Order parameters|order parameter]] as a descriptor of the essential character of the transition has proven transformative.