High-Temperature Analyticity of the Widom-Rowlinson Model with Finite Repulsion

The high-temperature behavior of the lattice version of the Widom-Rowlinson "$A-B$" model is studied, under the assumption of a finite repulsion $W$ between neighboring $A$ and $B$ molecules. Application of the extended Yang-Lee theorem shows the grand partition function (for the square lattice) to be analytic on the positive real axis for sufficiently high temperature ($\beta W<\mathrm{}\ln \left[2\right(2-\surd 2\left)\right]\simeq 0.158$).