The five-vertex model as a discrete log-gas
Filippo Colomo, Michelangelo Mannatzu, Andrei G. Pronko
TL;DR
This work provides a complete resolvent-based analysis of the five-vertex model with scalar-product boundary conditions by reformulating its partition function as a discrete log-gas. It derives the free-energy density in the scaling limit across both square ($\lambda=\mu$) and rectangular ($\lambda\neq\mu$) geometries, reproducing known leading-order results and delivering explicit forms for the log-gas resolvent in all regimes. The study reveals two third-order phase transitions at critical points $x_c$ (and its inverse in the square case), associated with changes between void, band, and saturated regions in the equilibrium measure, and demonstrates a robust framework to connect to limit-shape phenomena and potential boundary correlations via the tangent method. These results lay groundwork for determining Arctic curves and boundary correlation functions in the five-vertex model and related integrable systems.
Abstract
We consider the five-vertex model on a rectangular domain of the square lattice, with the so-called `scalar-product' boundary conditions. We address the evaluation of the free-energy density of the model in the scaling limit, that is when the number of sites is sent to infinity and the mesh of the lattice to zero, while keeping the size of the domain constant. To this aim, we reformulate the partition function of the model in terms of a discrete log-gas, and study its behaviour in the thermodynamic limit. We reproduce previous results, obtained by using a differential equation approach. Moreover, we provide the explicit form of the resolvent in all possible regimes. This work is preliminary to further studies of limit shape phenomena in the model.
