The regular embeddings of complete bipartite graphs Kn,n in orientable surfaces are classified 5 and enumerated, and their automorphism groups and combinatorial properties are determined. The method depends on earlier classifications in the cases where n is a prime power, obtained in collaboration with Du, Kwak, Nedela and Škoviera, together with results of Itô, Hall, Huppert and Wielandt on fa...

Characterizing regular covers of edge-transitive or arc-transitive graphs is currently a hot topic in algebraic graph theory. In this paper, we will classify arctransitive regular cyclic covers of the complete bipartite graph Kp,p for each odd prime p. The classification consists of four infinite families of graphs. In particular, such covers exist for each odd prime p. The regular elementary a...

In this article, we carry out the investigation for regular sequences of symmetric polynomials in the polynomial ring in three and four variable. Any two power sum element in C[x1,x2, . . . ,xn] for n ≥ 3 always form a regular sequence and we state the conjecture when pa, pb, pc for given positive integers a < b < c forms a regular sequence in C[x1,x2,x3,x4]. We also provide evidence for this c...

A complete partition of a graph is a partition of the vertex set such that any two classes are connected by an edge. We consider the problem of finding a complete partition maximizing the number of classes. This relates to clustering into the greatest number of groups so as to minimize the diameter (inter-cluster connectivity) without concern for the intra-cluster topology. We give a randomized...

It is shown that if G is any bipartite 2-regular graph of order at most n2 or at least n − 2, then the obvious necessary conditions are sufficient for the existence of a decomposition of the complete graph of order n into a perfect matching and edge-disjoint copies of G.

Let us think of such a tree (in which we take no account of the order among the sons of a node) as modelling the behaviour of a machine accepting symbols from, or submitting to observations by, its environment. In tree Tl only the symbol a may be accepted at the start (or, only the observation a may be made), after which b or c may be accepted. The tree is determinate, since no node has two out...

We extend order-sorted unification by permitting regular expression sorts for variables and in the domains of function symbols. The obtained signature corresponds to a finite bottom-up unranked tree automaton. We prove that regular expression order-sorted (REOS) unification is of type infinitary and decidable. The unification problem presented by us generalizes some known problems, such as, e.g...

in recent years, many changes have been observed in buying culture of customers and developing chain stores in iran. moreover, need to be more competition in business environments made necessary the stablishment of chain stores, the creation of competitive advantage and long relations to the costumers. regular marketing is a response to stores requirement when establishing such a win-win long r...