ENUMERATION OF ROOTED VERTEX NON-SEPARABLE PLANAR MAPS

In a rooted planar map, the rooted vertex is said to be non-separable if the vertex onthe boundary of the outer face as an induced graph is not a cut-vertex. In this paper, the author derives a functional equation satisfied by the enumeratingfuuction of rooted vertex non-separable planar maps dependent on the edge number and thenumber of the edges on the outer face boundary, finds a parametric expression of itssolution, and obtains an explicit formula for the function. Particularly, the number of rooted vertex non-separable maps only replying on theedge number and that of rooted vertex non-separable tree-like maps defined in [4] accordingto the two indices, the edge number and the number of the edges on the outer face boundary,or only one index, the edge number, are also determined.     

Fixed points of n-valued maps on surfaces and the Wecken property—a configuration space approach

In this paper, we explore the fixed point theory of n-valued maps using configuration spaces and braid groups, focusing on two fundamental problems, the Wecken property, and the computation of the Nielsen number. We show that the projective plane(resp. the 2-sphere S~2) has the Wecken property for n-valued maps for all n ∈ N(resp. all n 3). In the case n = 2 and S~2, we prove a partial result about the Wecken property.We then describe the Nielsen number of a non-split n-valued map ? : X■X of an orientable, compact manifold without boundary in terms of the Nielsen coincidence numbers of a certain finite covering q : X → X with a subset of the coordinate maps of a lift of the n-valued split map ? ? q : X■X.     

Klein瓶上的奇异地图

It is well known that singular maps (i. e. ,those have only one face on a surface)play a key role in the theory of up-embeddability of graphs. In this paper the number of rooted singular maps on the Klein bottle is studied. An explicit form of the enumerating function according to the root-valency and the size of the map is determined. Further ,an expression of the vertex partition function is also found.     

BISINGULAR MAPS ON SOME SURFACES

A map is bisingular if each edge is either a loop (This paper only considersplanar loop) or an isthmus (i.e., on the boundary of the same face). This paper studies thenumber of rooted bisingular maps on the sphere and the torus, and also presents formulaefor such maps with three parameters: the root-valency, the number of isthmus, and thenumber of planar loops.     

克莱茵瓶上奇异地图的色数

A map is singular if each edge is on the same face on a surface (i.e., it has only one face on a surface). In this paper we present the chromatic enumeration for rooted singular maps on the Klein bottle.     

Automorphisms of Maps with a Given Underlying Graph and Their Application to Enumeration

A graph is called a semi-regular graph if its automorphism group action on its ordered pair of adjacent vertices is semi-regular. In this paper, a necessary and sufficient condition for an automorphism of the graph F to be an automorphism of a map with the underlying graph F is obtained. Using this result, all orientation-preserving automorphisms of maps on surfaces (orientable and non-orientable) or just orientable surfaces with a given underlying semi-regular graph F are determined. Formulas for the numbers of non-equivalent embeddings of this kind of graphs on surfaces (orientable, non-orientable or both) are established, and especially, the non-equivalent embeddings of circulant graphs of a prime order on orientable, non-orientable and general surfaces are enumerated.     

INEQUALITY OF KORN‘S TYPE ON COMPACT SURFACES WITHOUT BOUNDARY

Inequalities of Korn's type on a surface with boundary have been proved in many papers using different techniques (see e.g. [4, 5, 11]). The author proves here an inequality of Korn's type on a compact surface without boundary. The idea is to use a finite number of maps for defining the surface and the inequality of Korn's type without boundary conditions for every map and to recast these in a general functional analysis setting about quotient spaces.     

On surfaces immersed in Euclidean space R~4 Dedicated to Professor Yang Lo on the Occasion of his 70th Birthday

Let M be a closed oriented surface immersed in R4 . Associated it one has the generalized Gauss map from M into the Grassmann manifold G 4,2 . This note will be concerned with the geometry of the generalized Gauss map by using the moving frame theory and the quaternion interpretation of Plcker coordinates. As one of consequences,we get the celebrated theorem of Chern and Spanier,Hoffman and Osserman,who proved it by quite different methods. At last,we give an explicit construction of a series of immersions of S2 in R4 with any given normal Euler number.     

Counting rooted maps by Genus. I

Using a combinatorial equivalent for maps, we take the first census of maps on orientable surfaces of arbitrary genus. We generalize to higher genus Tutte's recursion formula for counting slicings, and thus obtain an algorithm for counting rooted maps by genus, number of edges, and number of vertices. We then solve a special case of this recursion formula, to count slicngs with one face by genus. This leads to an explicit formula which counts rooted maps with one face by genus and number of edges.     

The Semi-Arc Automorphism Group of a Graph with Application to Map Enumeration

A map is a connected topological graph cellularly embedded in a surface. For a given graph Γ, its genus distribution of rooted maps and embeddings on orientable and non-orientable surfaces are separately investigated by many researchers. By introducing the concept of a semi-arc automorphism group of a graph and classifying all its embeddings under the action of its semi-arc automorphism group, we find the relations between its genus distribution of rooted maps and genus distribution of embeddings on orientable and non-orientable surfaces, and give some new formulas for the number of rooted maps on a given orientable surface with underlying graph a bouquet of cycles B_n, a closed-end ladder L_n or a Ringel ladder R_n. A general scheme for enumerating unrooted maps on surfaces(orientable or non-orientable) with a given underlying graph is established. Using this scheme, we obtained the closed formulas for the numbers of non-isomorphic maps on orientable or non-orientable surfaces with an underlying bouquet B_n in this paper.     

Archimedean solids of genus two

The problem of classifying orientable vertex-transitive maps on a surface with genus two is considered. We construct and classify all simple orientable vertex-transitive maps, with face width at least 3 which can be viewed as generalisations of classical Archimedean solids. The proof is computer-aided. The developed method applies to higher genera as well.     

射影平面和环面上奇异地图的色和

一个地图的每条边,若在同一面的边界上,则称它为奇异地图．由于含环的地图是不可着色的,本文所有地图均不含环．本文研究射影平面和环面上带根奇异地图的色和．     

Classical curves via one-vertex maps

One-vertex maps (a type of dessin d’enfant) give a uniform characterization of certain well-known algebraic curves, including those of Klein, Wiman, Accola–Maclachlan and Kulkarni. The characterization depends on a new classification of one-vertex (dually, one-face or unicellular) maps according to the size of the group of map automorphisms. We use an equivalence relation appropriate for studying the faithful action of the absolute Galois group on dessins, although we do not pursue that line of inquiry here.     

A sequence representation for maps

An easy implementable polynomial algorithm to test for isomorphism of graphs embedded in arbitrary compact surfaces (maps) is given.

The map are defined algebraically by Tutte's axtom system. We produce a canonical codification of them as a sequence of 4e integers (2e if the map is orientable) where e is the number of edges. To test for isomorphism between two maps we just have to compare their codes.

Some applications relying on the implementation are given.     

可定向闭曲面上保定向的周期映射

讨论可定向闭曲面上保定向周期映射的共轭类分类问题.Kulkarni(1997)指出:亏格g大于3时,曲面上任意周期大于或等于4g的周期映射共轭于两类周期映射中某个映射的幂.之后Hirose(2010)得到:亏格g大于12时,曲面上任意周期大于或等于3g的周期映射共轭于4类周期映射中某个映射的幂.本文在此基础上研究了周期大于或等于3(g-1)的情形:当亏格g大于21时,得到了和Hirose相似的结论,且找出了更多不能被包含在前面所讲的4类周期映射中的情形.     

Counting rooted maps by genus III: Nonseparable maps

A map on an orientable surface is called separable if its underlying graph can be disconnected by splitting a vertex into two pieces, each containing a positive number of edge-ends consecutively ordered with respect to counter-clockwise rotation around the original vertex. This definition is shown to be equivalent for planar maps to Tutte's definition of a separable planar map. We develop a procedure for determining the generating functions N_g,b(x) = Σ_p=0^∞n_g,b,px^p, where n_g,b,p is the number of rooted nonseparable maps with b + p edges and p + 1 vertices on an orientable surface of genus g. Similar results are found for tree-rooted maps.     

Trading crossings for handles and crosscaps

Let c_k = cr_k (G) denote the minimum number of edge crossings when a graph G is drawn on an orientable surface of genus k. The (orientable) crossing sequence c_o, c₁,c₂…encodes the trade‐off between adding handles and decreasing crossings. We focus on sequences of the type c_o > c₁ > c₂ = 0; equivalently, we study the planar and toroidal crossing number of doubly‐toroidal graphs. For every ? > 0 we construct graphs whose orientable crossing sequence satisfies c₁/c_o > 5/6??. In other words, we construct graphs where the addition of one handle can save roughly 1/6th of the crossings, but the addition of a second handle can save five times more crossings. We similarly define the non‐orientable crossing sequence ?₀,?₁,?₂, ··· for drawings on non‐orientable surfaces. We show that for every ?₀ > ?₁ > 0 there exists a graph with non‐orientable crossing sequence ?₀, ?₁, 0. We conjecture that every strictly‐decreasing sequence of non‐negative integers can be both an orientable crossing sequence and a non‐orientable crossing sequence (with different graphs). © 2001 John Wiley & Sons, Inc. J Graph Theory 38: 230–243, 2001