Vertex volumes, lattice-minima tails, and height zeta functions for the standard arithmetic quotient of ${\mathrm{PGL}}_d$

Abstract

We study the standard nonuniform arithmetic quotient of the affine Bruhat--Tits building attached to ${\mathrm{PGL}}_d({\mathbb{F}}_q((t^{-1})))$, with Haar measure normalized so that a maximal compact subgroup has volume one. We first compute its vertex volume in closed product form. The proof is entirely building-theoretic: vertices are parametrized by a dominant sector, their stabilizers are counted exactly, and the resulting sum over block compositions is evaluated by a cut-set recursion. On the same quotient, we introduce a homothety-invariant normalized lattice-minima height $\alpha$. We determine its exact integrability threshold, proving that $\alpha$ belongs to $L^r$ precisely for $0<r<d$, and establish a sharp cusp-tail estimate of order $T^{-d}$. The associated positive-moment height zeta function, equivalently the Mellin transform of the cusp-height distribution, converges exactly in the half-plane $\mathrm{Re}(s)<d$. It admits a meromorphic continuation as a rational function of $q^{s/d}$ and has a simple pole at $s=d$, with an explicit critical coefficient. We also compute the resulting rational functions explicitly for $d=3,4,5$. Thus the same dominant-sector coordinates simultaneously control volume, cusp decay, and the analytic structure of the height zeta function.

22 pages, comments welcome!