Enumeration of Hypermaps of a Given Genus

TL;DR

This paper develops enumeration methods for rooted and unrooted hypermaps of a fixed genus, providing functional equations and explicit formulas for counting hypermaps by various parameters.

Contribution

It introduces functional equations for multirooted hypermaps and derives explicit generating functions for low-genus hypermaps, advancing combinatorial enumeration techniques.

Findings

Derived functional equations for multirooted hypermaps.

Obtained parametric expressions for low-genus hypermap generating functions.

Counted unrooted hypermaps by multiple parameters.

Abstract

This paper addresses the enumeration of rooted and unrooted hypermaps of a given genus. For rooted hypermaps the enumeration method consists of considering the more general family of multirooted hypermaps, in which darts other than the root dart are distinguished. We give functional equations for the generating series counting multirooted hypermaps of a given genus by number of darts, vertices, edges, faces and the degrees of the vertices containing the distinguished darts. We solve these equations to get parametric expressions of the generating functions of rooted hypermaps of low genus. We also count unrooted hypermaps of given genus by number of darts, vertices, hyperedges and faces.