Leading Fisher Partition Function Zeros as Indicators of Structural Transitions in Macromolecules

We show that leading zeros, i.e., isolated complex zeros of the canonical partition function near the positive real axis, are robust indicators of conformational transitions in finite macromolecular systems. For a flexible polymer with 250 monomers, we calcu- late the complex Fisher partition function zeros from a precise estimate of the density of states that was obtained via advanced multicanonical Monte Carlo simulations. Transition temperatures estimated from the leading zeros correspond very well to regions of enhanced thermal activity as signaled by canonical thermodynamic quantities such as the specific heat and fluctuations of the radius of gyration.