# Compatible Cycles and CHY Integrals

## TL;DR

This paper explores the extension of CHY integral computations to pairs of arbitrary 2-regular graphs by constructing compatible cycles, providing lower bounds and connections to breakpoint graphs.

## Contribution

It introduces the concept of compatible cycles for extending CHY integrals and proves a lower bound on their number for any 2-regular graph.

## Key findings

- At least (n-2)!/4 compatible cycles exist for any 2-regular graph.
- A connection is established between compatible cycles and breakpoint graphs with double edges.
- The lower bound for compatible cycles is compared to the super Catalan numbers for basis generation.

## Abstract

The CHY construction naturally associates a vector in $\mathbb{R}^{(n-3)!}$ to every 2-regular graph with $n$ vertices. Partial amplitudes in the biadjoint scalar theory are given by the inner product of vectors associated with a pair of cycles. In this work we study the problem of extending the computation to pairs of arbitrary 2-regular graphs. This requires the construction of compatible cycles, i.e. cycles such that their union with a 2-regular graph admits a Hamiltonian decomposition. We prove that there are at least $(n-2)!/4$ such cycles for any 2-regular graph. We also find a connection to breakpoint graphs when the graph only has double edges. We end with a comparison of the lower bound on the number of randomly selected cycles needed to generate a basis of $\mathbb{R}^{(n-3)!}$, using the super Catalan numbers, and our lower bound for compatible cycles.