Notes on Worldsheet-Like Variables for Cluster Configuration Spaces

TL;DR

This paper investigates worldsheet-like variables within cluster configuration spaces, especially of type D, deriving them systematically from Y-systems, and explores their applications in understanding space boundaries, topological properties, and related conjectures.

Contribution

It provides a systematic derivation of worldsheet-like variables for cluster algebras, especially type D, and applies them to analyze configuration space boundaries and topological features.

Findings

Derived dihedral coordinates from Y-systems for type D

Expressed cluster string integrals in compact forms

Proposed conjectures on space point counts and cohomology dimensions

Abstract

We continue the exploration of various appearances of cluster algebras in scattering amplitudes and related topics in physics. The cluster configuration spaces generalize the familiar moduli space ${\mathcal M}_{0,n}$ to finite-type cluster algebras. We study worldsheet-like variables, which for classical types have also appeared in the study of the symbol alphabet of Feynman integrals. We provide a systematic derivation of these variables from $Y$-systems, which allows us to express the dihedral coordinates in terms of them and to write the corresponding cluster string integrals in compact forms. We mainly focus on the $D_n$ type and show how to reach the boundaries of the configuration space, and write the saddle-point equations in terms of these variables. Moreover, these variables make it easier to study various topological properties of the space using a finite-field method. We propose conjectures about quasi-polynomial point count, dimensions of cohomology, and the number of saddle points for the $D_n$ space up to $n=10$, which greatly extend earlier results.