Chamber zeta function and closed galleries in the standard non-uniform complex from $\operatorname{PGL}_3$
Soonki Hong, Sanghoon Kwon
TL;DR
This work defines and analyzes the type-1 chamber zeta function for the standard non-uniform arithmetic quotient $ extGammaackslasholdsymbol{eta}$ of the Bruhat–Tits building of $ ext{PGL}_3(F)$. It extends the Ihara–Bass framework to a higher-rank, non-uniform setting by introducing a chamber transfer operator $T$ on type-1 pointed chambers and proving a determinant formula $Z_ extGamma(u)=igl( ext{det}(I-uT)igr)^{-1}$, establishing rationality of the zeta function. The authors provide explicit counting results for closed gallery classes, derive the generating function for the weighted counts $N_m$, and give a finite-rank truncation analysis that yields a concrete rational expression for $Z_ extGamma(u)$. They also discuss spectral and Hecke-theoretic perspectives, highlighting potential connections to automorphic $L$-functions and suggesting avenues for generalization to higher rank and other non-uniform complexes.
Abstract
We introduce the \emph{chamber zeta function} for a complex of groups, defined via an Euler product over primitive tailless chamber galleries, extending the Ihara--Bass framework from weighted graphs to higher-rank settings. Let $\mathcal{B}$ be the Bruhat--Tits building of $\mathrm{PGL}_{3}(F)$ for a non-archimedean local field $F$ with residue field $\mathbb{F}_{q}$. For the standard arithmetic quotient $Γ\backslash\mathcal{B}$ with $Γ=\mathrm{PGL}_{3}(\mathbb{F}_{q}[t])$, we prove an Ihara--Bass type \emph{determinant formula} expressing the chamber zeta function as the reciprocal of a characteristic polynomial of a naturally defined chamber transfer operator. In particular, the chamber zeta function is \emph{rational} in its complex parameter. As an application of the determinant formula, we obtain explicit counting results for closed gallery classes arising from tailless galleries in $\mathcal{B}$, including exact identities and spectral asymptotics governed by the chamber operator.
