Zeros of the partition function for a continuum system at first order   transitions
  We extend the circle theorem on the zeros of the partition function to a continuum system. We also calculate the exact zeros of the partition function for a finite system where the probability distribution for the order parameter is given by two asymmetric Gaussian peaks. For the temperature driven first order transition in the thermodynamic limit, the locus and the angular density of zeros are given by $r = e^{(\Delta c/2l)\theta^2}$ and $2\pi g(\theta)=l(1+\frac{3}{2}(\Delta c/l)^2\theta^2)$ respectively in the complex $z(\equiv re^{i\theta})$-plane where $l$ is the reduced latent heat, $\Delta c$ is the discontinuity in the reduced specific heat and $z= \exp(1-T_c/T)$. 
Koo-Chul Lee