an:06986902
Zbl 1400.05019
Krasko, Evgeniy; Omelchenko, Alexander
Enumeration of \(r\)-regular maps on the torus. I: Rooted maps on the torus, the projective plane and the Klein bottle. Sensed maps on the torus
EN
Discrete Math. 342, No. 2, 584-599 (2019).
00423496
2019
j
05A15
map; surface; orbifold; unlabelled enumeration
Summary: The work that consists of two parts is devoted to the problem of enumerating unrooted \(r\)-regular maps on the torus up to all its symmetries. We begin with enumerating near-\(r\)-regular rooted maps on the torus, the projective plane and the Klein bottle, as well as some special kinds of maps on the sphere: near-\(r\)-regular maps, maps with multiple leaves and maps with multiple root darts. For \(r = 3\) and \(r = 4\) we obtain exact analytical formulas. For larger \(r\) we derive recurrence relations. Then we enumerate \(r\)-regular maps on the torus up to homeomorphisms that preserve its orientation -- so-called sensed maps. Using the concept of a quotient map on an orbifold we reduce this problem to enumeration of certain above-mentioned classes of rooted maps. For \(r = 3\) and \(r = 4\) we obtain closed-form expressions for the numbers of \(r\)-regular sensed maps by edges. All these results will be used in the second part of the work to enumerate \(r\)-regular maps on the torus up to all homeomorphisms -- so-called unsensed maps.