Tricriticality

Abstract The phase diagram of a model of interacting polygons (or walks) may include a tricritical point, which makes an understanding of tricriticality essential if the thermodynamic nature of interacting polygons is considered. In the case of the models described in this monograph, the theory of tricriticality will give a framework for the description of the (intuitive) phase behaviour expected from a typical interacting model. In this respect it is very useful, since it guides numerical and mathematical approaches to the models in general. It is important not to forget that tricriticality is not mathematically rigorous, but is based on a large number of assumptions which form a belief-system within which models are described. The basic theory of tricriticality was reviewed extensively by I.D. Lawrie and S. Sarlbach [225], see also R. Brak, A.L. Owczarek and T. Prellberg [34].