Zeta renormalization and pressure at infinity for an infinitely cusped tree lattice

Abstract

We study weighted periodic-orbit zeta functions for an infinitely cusped tree lattice $Y_q$, where $q\ge 2$ is even and the quotient is a one-sided comb. The global Euler product fails coefficientwise because infinitely many primitive cycles have length four. A first-return determinant at a finite directed-edge set nevertheless exists, and stationary Schur elimination gives an algebraic formula for the root local zeta and its dominant poles. For the two-step multiplicity potential we compute the Gurevich pressure $P_G=2\log (q+1)$ and pressure at infinity $P_{\infty }=\log (4q)$, yielding strong positive recurrence and exponential local-orbit asymptotics. The height-damped transition operator is trace class. After subtraction of an explicit integrated-pressure counterterm, the inverse Fredholm determinant has a locally uniform finite part, expressed by a convergent dilogarithmic product and covariant under changes of height.

34 pages, 1 figure, 3 tables