The cluster complex for cluster Poisson varieties and representations of acyclic quivers

Abstract

Let $\mathcal{X}$ be a skew-symmetrizable cluster Poisson variety. The cluster complex $\Delta^+(\mathcal{X})$ was introduced by Gross, Hacking, Keel and Kontsevich. It codifies the theta functions on $\mathcal{X}$ that restrict to a character of a seed torus. Every seed ${ \bf s}$ for $\mathcal{X}$ determines a fan realization $\Delta^+_{\bf s}(\mathcal{X})$ of $\Delta^+(\mathcal{X})$. For every ${\bf s}$ we provide a simple and explicit description of the cones of $\Delta^+_{{\bf s}}(\mathcal{X})$ and their facets using ${\bf c}$-vectors. Moreover, we give formulas for the theta functions parametrized by the integral points of $\Delta^+_{{ \bf s}}(\mathcal{X})$ in terms of $F$-polynomials. In case $\mathcal{X}$ is skew-symmetric and the quiver $Q$ associated to ${\bf s}$ is acyclic, we describe the normal vectors of the supporting hyperplanes of the cones of $\Delta^+_{\bf s}(\mathcal{X})$ using ${\bf g}$-vectors of (non-necessarily rigid) objects in $\mathsf{K}^{\rm b}(\text{proj} \; kQ)$.