dc.contributor.author Grimmett, Geoffrey en dc.contributor.author Li, Zhongyang en dc.date.accessioned 2016-02-25T11:13:15Z dc.date.available 2016-02-25T11:13:15Z dc.date.issued 2017 en dc.identifier.citation Grimmett et al. Contemporary Mathematics (2016) en dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/254013 dc.description.abstract The current paper is a short review of rigorous results for the 1-2 model. The 1-2 model on the hexagonal lattice is a model of statistical mechanics in which each vertex is constrained to have degree either 1 or 2. It was proposed in a study by Schwartz and Bruck of constrained coding systems, and is strongly connected to the dimer model on a decoration of the lattice, and to an enhanced Ising model and an associated polygon model on the graph derived from the hexagonal lattice by adding a further vertex in the middle of each edge. The general 1-2 model possesses three parameters a, b, c. The fundamental technique is to represent probabilities of interest as ratios of counts of dimer coverings of certain associated graphs, and to apply the Pfaffian method of Kasteleyn, Fisher, and Temperley. Of special interest is the existence (or not) of phase transitions. It turns out that all clusters of the infinite-volume limit are almost surely finite. On the other hand, the existence (with strictly positive probability) of infinite ‘homogeneous’ clusters, containing vertices of given type, depends on the values of the parameters. A further type of phase transition emerges in the study of the two-edge correlation function, and in this case the critical surface may be found explicitly. For instance, when a ≥ b ≥ c > 0, the surface given by √ a = √ b + √ c is critical. en dc.language.iso en en dc.publisher American Mathematical Society en dc.rights Attribution-NonCommercial-NoDerivs 2.0 UK: England & Wales dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/2.0/uk/ dc.subject 1-2 model en dc.subject dimers en dc.subject polygon model en dc.subject Ising model en dc.subject perfect matching en dc.subject Kasteleyn matrix en dc.subject phase transition en dc.subject percolation en dc.title The 1-2 model en dc.type Book chapter prism.endingPage 152 prism.publicationDate 2017 en prism.publicationName In the Tradition of Ahlfors–Bers, VII en prism.startingPage 130 prism.volume 696 en dc.rioxxterms.funder EPSRC dc.rioxxterms.projectid EP/103372X/1 rioxxterms.versionofrecord 10.1090/conm/696 en rioxxterms.licenseref.uri http://www.rioxx.net/licenses/all-rights-reserved en rioxxterms.licenseref.startdate 2017 en dc.contributor.orcid Grimmett, Geoffrey [0000-0001-7646-3368] rioxxterms.type Book chapter en
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