Partition Function Zeroes

Lee and Yang were the first to  realize that extending the partition function of a statistical mechanical model into the complex plane gave a useful way of understanding how the non-analyticities that characterize phase transitions could emerge from lattice models in the thermodynamic limit. Their work considered field driven transitions and was extended by Fisher to thermal transitions.  The scaling of the density of the partition function zeroes that arises in such an approach gives a useful alternative method for extracting the critical properties  of phase transitions and deciding their nature.