Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2015, Tutor: Tomeu Fiol
We present the Lee-Yang theory that links the study of phase transitions to the localization of zeros in the complex fugacity plane. We prove the Lee-Yang theorem using Asano's contraction method and we apply it for the one and two dimensional Ising model. We also show that the Lee-Yang formalism can shed some light on the di cult task of counting the number of ground states in supersymmetric theories.