Weak Hopf Algebra and Its Quiver Representation

This study induced a weak Hopf algebra from the path coalgebra of a weak Hopf quiver. Moreover, it gave a quiver representation of the said algebra which gives rise to the various structures of the so-called weak Hopf algebra through the quiver. Furthermore, it also showed the canonical representation for each weak Hopf quiver. It was further observed that a Cayley digraph of a Clifford monoid can be embedded in its corresponding weak Hopf quiver of a Clifford monoid. This lead to the development of the foundation structures of weak Hopf algebra. Such quiver representation is useful for the classification of its path coalgebra. Additionally, some structures of module theory of algebra were also given. Such algebras can also be applied for obtaining the solutions of “quantum Yang–Baxter equation” that has many applications in the dynamical systems for finding interesting results.

On the asymptotic enumeration of Cayley graphs

In this paper, we are interested in the asymptotic enumeration of Cayley graphs. It has previously been shown that almost every Cayley digraph has the smallest possible automorphism group: that is, it is a digraphical regular representation (DRR). In this paper, we approach the corresponding question for undirected Cayley graphs. The situation is complicated by the fact that there are two infinite families of groups that do not admit any graphical regular representation (GRR). The strategy for digraphs involved analysing separately the cases where the regular group R has a nontrivial proper normal subgroup N with the property that the automorphism group of the digraph fixes each N-coset setwise, and the cases where it does not. In this paper, we deal with undirected graphs in the case where the regular group has such a nontrivial proper normal subgroup.

Hermitian Adjacency Spectrum of Cayley Digraphs over Dihedral Group

We first study the spectrum of Hermitian adjacency matrix (H-spectrum) of Cayley digraphs X(D2n, S) on dihedral group D2n with |S| = 3. Then we show that all Cayley digraphs X(D2p, S) with |S| = 3 and p odd prime are Cay-DS, namely, for any Cayley digraph X(D2p, T), X(D2p, T) and X(D2p, S) having the same H-spectrum implies that they are isomorphic.

Domination of Cayley Digraph and its Complement

A Cayley graph constructed out of a group Γ and its generating set A is denoted by Cay (Γ, A). The digraph with the same node set as the original digraph is said to be a complement digraph if it has an edge from x to y exactly when the original digraph does not have an edge from x to y. A subset Ɖ of V is called a dominating set if each vertex in V- Ɖ is adjacent to at least one vertex in Ɖ. The minimum cardinality of a dominating set is called Domination number which is denoted by γ. The domination number of Cayley digraphs and Complement of Cayley digraphs of groups are investigated in this paper. Also, the graph relationship involving domination parameters in a graph and its complement are studied.

Pentavalent Symmetric Graphs of Order Twice a Prime Square

A classification of pentavalent symmetric graphs of order twice a prime square is given. It is proved that such a graph is a coset graph of ℤ3. A 6 (non-split extension), or a bi-coset graph of an extra-special group of order 125, or the standard double cover of a specific abelian Cayley digraph of order a prime square.

On Cayley Digraphs That Do Not Have Hamiltonian Paths

We construct an infinite family {Cay→(Gi;ai;bi)} of connected, 2-generated Cayley digraphs that do not have hamiltonian paths, such that the orders of the generators ai and bi are unbounded. We also prove that if G is any finite group with |[G,G]|≤3, then every connected Cayley digraph on G has a hamiltonian path (but the conclusion does not always hold when |[G,G]|=4 or 5).

On the Characteristic Polynomial of $n$-Cayley Digraphs

A digraph $\Gamma$ is called $n$-Cayley digraph over a group $G$‎, ‎if there exists a semiregular subgroup $R_G$ of Aut$(\Gamma)$ isomorphic to $G$ with $n$ orbits‎. ‎In this paper‎, ‎we represent the adjacency matrix of $\Gamma$ as a diagonal block‎ ‎matrix in terms of irreducible representations of $G$ and determine its characteristic polynomial‎. ‎As corollaries of this result we find‎: ‎the spectrum of semi-Cayley graphs over abelian groups‎, ‎a relation between the characteristic polynomial of an $n$-Cayley graph and its complement‎, ‎and the spectrum of‎ ‎Calye graphs over groups with cyclic subgroups‎. ‎Finally we determine the eigenspace of $n$-Cayley digraphs and their main eigenvalues‎.

Random Cayley digraphs of diameter 2 and given degree

Graph Theory International audience We consider random Cayley digraphs of order n with uniformly distributed generating sets of size k. Specifically, we are interested in the asymptotics of the probability that such a Cayley digraph has diameter two as n -> infinity and k = f(n), focusing on the functions f(n) = left perpendicularn(delta)right perpendicular and f(n) = left perpendicularcnright perpendicular. In both instances we show that this probability converges to 1 as n -> infinity for arbitrary fixed delta is an element of (1/2, 1) and c is an element of (0, 1/2), respectively, with a much larger convergence rate in the second case and with sharper results for Abelian groups.

Explicit Cayley Covers of Kautz Digraphs

Given a finite set $V$ and a set $S$ of permutations of $V$, the group action graph $\mathrm{GAG}(V,S)$ is the digraph with vertex set $V$ and arcs $(v,v^\sigma)$ for all $v\in V$ and $\sigma\in S$. Let $\langle S\rangle$ be the group generated by $S$. The Cayley digraph $\textrm{Cay}(\langle S\rangle, S)$ is called a Cayley cover of $\mathrm{GAG}(V,S)$. We define the Kautz digraphs as group action graphs and give an explicit construction of the corresponding Cayley cover. This is an answer to a problem posed by Heydemann in 1996.