Let F be a finite simple undirected graph with no isolated vertices. Let p, q be prime numbers with p≥q. We complete the classification of the graphs on which a group of order pq acts edge-transitively. The results a...Let F be a finite simple undirected graph with no isolated vertices. Let p, q be prime numbers with p≥q. We complete the classification of the graphs on which a group of order pq acts edge-transitively. The results are the following. If Aut（Г） contains a subgroup G of order pq that acts edge-transitively on F, then F is one of the following graphs： （1） pK1,1; （2） pqK1,1; （3） pgq,1; （4） qKp,1 （p 〉 q）; （5） pCq （q 〉 2）; （6） qCp （p 〉 q）; （7） Cp （p 〉 q = 2）; （8） Cpq; （9） （Zp, C） whereC={±r^μ ｜μ∈Zq} withq〉2, q｜（p-1） and r≠1≡r^q （modp）; （10） Kp,1 （p 〉 q）; （11） a double Cayley graph B（G,C） with C = {1-r^μ ｜ μ ∈ Zq} and r≠1≡r^q （modp）; （12） Kpq,1;or （13） Kp,q.展开更多
Let Г=Cay(G,S)be the Cayley graph of a group G with respect to its subset S.The graph is said to be normal edge-transitive if the normalizer of G in the automorphism group Aut(T)of F acts transitively on the edge set...Let Г=Cay(G,S)be the Cayley graph of a group G with respect to its subset S.The graph is said to be normal edge-transitive if the normalizer of G in the automorphism group Aut(T)of F acts transitively on the edge set of ГIn this paper,we study the structure of normal edge-transitive Cayley graphs on a class of non-abelian groups with order 2p^(2)(p refers to an odd prime).The structure and automorphism groups of the non-abelian groups are first presented,and then the tetravalent normal edge-transitive Cayley graphs on such groups are investigated.Finally,the normal edge-transitive Cayley graphs on group G are characterized and classified.展开更多
We determine all connected normal edge-transitive Cayley graphs on non-abelian groups with order 4p, where p is a prime number. As a consequence we prove if IGI = 25p, δ = 0, 1, 2 and p prime, then F 1 Cay（G, S） i...We determine all connected normal edge-transitive Cayley graphs on non-abelian groups with order 4p, where p is a prime number. As a consequence we prove if IGI = 25p, δ = 0, 1, 2 and p prime, then F 1 Cay（G, S） is a connected normal 1/2 arc-transitive Cayley graph only if G = F4p, where S is an inverse closed generating subset of G which does not contain the identity element of G and F4p is a group with presentation F4p = （a, b ｜aP = b4 = 1, b-lab = a^λ）, where λ2 = -1 （mod p）.展开更多
A graph is called edge-transitive if its full automorphism group acts transitively on its edge set.In this paper,by using classification of finite simple groups,we classify tetravalent edge-transitive graphs of order ...A graph is called edge-transitive if its full automorphism group acts transitively on its edge set.In this paper,by using classification of finite simple groups,we classify tetravalent edge-transitive graphs of order p2q with p,q distinct odd primes.The result generalizes certain previous results.In particular,it shows that such graphs are normal Cayley graphs with only a few exceptions of small orders.展开更多
P Kulasinghe and S Bettayeb showed that any multiply-twisted hypercube withfive or more dimensions is not vertex-transitive. This note shows that any multiply-twistedhypercube with four or less dimensions is vertex-tr...P Kulasinghe and S Bettayeb showed that any multiply-twisted hypercube withfive or more dimensions is not vertex-transitive. This note shows that any multiply-twistedhypercube with four or less dimensions is vertex-transitive, and that any multiply-twistedhypercube with three or larger dimensions is not edge-transitive.展开更多
A regular edge-transitive graph is said to be semisymmetric if it is mot vertex-transitive. By Folkman [J. Combin. Theory 3 （1967）, 215-232], there is no semisymmetric graph of order 2p or 2p^2 for a prime p, and by...A regular edge-transitive graph is said to be semisymmetric if it is mot vertex-transitive. By Folkman [J. Combin. Theory 3 （1967）, 215-232], there is no semisymmetric graph of order 2p or 2p^2 for a prime p, and by Malni6 et al. [Discrete Math. 274 （2004）, 18-198], there exists a unique cubic semisymmetrie graph of order 2p3, the so called Gray graph of order 54. In this paper, it is shown that there is no connected cubic semisymmetric graph of order 4p^3 and that there exists a unique cubic semisymmetric graph of order 8p3, which is a Z2 × Z2-covering of the Gray graph.展开更多
A regular edge-transitive graph is said to be semisymmetric if it is not vertex-transitive.Let p be a prime.By Folkman[J.Combin.Theory 3(1967),215–232],there is no cubic semisymmetric graph of order 2p or 2p^2,and by...A regular edge-transitive graph is said to be semisymmetric if it is not vertex-transitive.Let p be a prime.By Folkman[J.Combin.Theory 3(1967),215–232],there is no cubic semisymmetric graph of order 2p or 2p^2,and by Hua et al.[Science in China A 54(2011),1937–1949],there is no cubic semisymmetric graph of order 4p^2.Lu et al.[Science in China A 47(2004),11–17]classified connected cubic semisymmetric graphs of order 6p^2.In this paper,for p>q≥5 two distinct odd primes,it is shown that the sufficient and necessary conditions which a connected cubic edge transitive bipartite graph of order 2qp^2 is semisymmetric.展开更多
Let Γ be a connected regular bipartite graph of order 18 p, where p is a prime. Assume that Γ admits a group acting primitively on one of the bipartition subsets of Γ. Then, in this paper, it is shown that eitherΓ...Let Γ be a connected regular bipartite graph of order 18 p, where p is a prime. Assume that Γ admits a group acting primitively on one of the bipartition subsets of Γ. Then, in this paper, it is shown that eitherΓ is arc-transitive, or Γ is isomorphic to one of 17 semisymmetric graphs which are constructed from primitive groups of degree 9p.展开更多
Let p be a prime.In this paper,a complete classification of edge-transitive N-covers of a cubic symmetric graph of order 2p is given for the case when N is a twogenerator 2-group whose derived subgroup is either isomo...Let p be a prime.In this paper,a complete classification of edge-transitive N-covers of a cubic symmetric graph of order 2p is given for the case when N is a twogenerator 2-group whose derived subgroup is either isomorphic to Z_(2)^(3)or generated by at most two elements.As an application,it is shown that 11 is the smallest value of n for which there exist infinitely many cubic semisymmetric graphs with order of the form 2^(n)p.展开更多
A graph F is called G-locally-quasiprimitive if each normal subgroup of Gv acts on F（v） trivially or transitively for every vertex v. In this paper we analyse the global action and the structural information of such...A graph F is called G-locally-quasiprimitive if each normal subgroup of Gv acts on F（v） trivially or transitively for every vertex v. In this paper we analyse the global action and the structural information of such groups G, extending the previous results for locally-primitive graphs and vertex-transitive locally-quasiprimitive graphs.展开更多
基金Supported by the NNSF of China (60776810,10871205)the NSF of Tianjin (08JCYBJC13900)the KYS of CAUC (09CAUC-S02)
文摘Let F be a finite simple undirected graph with no isolated vertices. Let p, q be prime numbers with p≥q. We complete the classification of the graphs on which a group of order pq acts edge-transitively. The results are the following. If Aut（Г） contains a subgroup G of order pq that acts edge-transitively on F, then F is one of the following graphs： （1） pK1,1; （2） pqK1,1; （3） pgq,1; （4） qKp,1 （p 〉 q）; （5） pCq （q 〉 2）; （6） qCp （p 〉 q）; （7） Cp （p 〉 q = 2）; （8） Cpq; （9） （Zp, C） whereC={±r^μ ｜μ∈Zq} withq〉2, q｜（p-1） and r≠1≡r^q （modp）; （10） Kp,1 （p 〉 q）; （11） a double Cayley graph B（G,C） with C = {1-r^μ ｜ μ ∈ Zq} and r≠1≡r^q （modp）; （12） Kpq,1;or （13） Kp,q.
文摘Let Г=Cay(G,S)be the Cayley graph of a group G with respect to its subset S.The graph is said to be normal edge-transitive if the normalizer of G in the automorphism group Aut(T)of F acts transitively on the edge set of ГIn this paper,we study the structure of normal edge-transitive Cayley graphs on a class of non-abelian groups with order 2p^(2)(p refers to an odd prime).The structure and automorphism groups of the non-abelian groups are first presented,and then the tetravalent normal edge-transitive Cayley graphs on such groups are investigated.Finally,the normal edge-transitive Cayley graphs on group G are characterized and classified.
文摘We determine all connected normal edge-transitive Cayley graphs on non-abelian groups with order 4p, where p is a prime number. As a consequence we prove if IGI = 25p, δ = 0, 1, 2 and p prime, then F 1 Cay（G, S） is a connected normal 1/2 arc-transitive Cayley graph only if G = F4p, where S is an inverse closed generating subset of G which does not contain the identity element of G and F4p is a group with presentation F4p = （a, b ｜aP = b4 = 1, b-lab = a^λ）, where λ2 = -1 （mod p）.
基金supported by National Natural Science Foundation of China (Grant Nos.11071210 and 11171292)
文摘A graph is called edge-transitive if its full automorphism group acts transitively on its edge set.In this paper,by using classification of finite simple groups,we classify tetravalent edge-transitive graphs of order p2q with p,q distinct odd primes.The result generalizes certain previous results.In particular,it shows that such graphs are normal Cayley graphs with only a few exceptions of small orders.
基金Supported by ANSF(01046102)Supported by the NNSF of China(10271114)
文摘P Kulasinghe and S Bettayeb showed that any multiply-twisted hypercube withfive or more dimensions is not vertex-transitive. This note shows that any multiply-twistedhypercube with four or less dimensions is vertex-transitive, and that any multiply-twistedhypercube with three or larger dimensions is not edge-transitive.
基金supported by National Natural Science Foundation of China (Grant No.10871021)the Specialized Research Fund for the Doctoral Program of Higher Education in China (Grant No.20060004026)
文摘A regular edge-transitive graph is said to be semisymmetric if it is mot vertex-transitive. By Folkman [J. Combin. Theory 3 （1967）, 215-232], there is no semisymmetric graph of order 2p or 2p^2 for a prime p, and by Malni6 et al. [Discrete Math. 274 （2004）, 18-198], there exists a unique cubic semisymmetrie graph of order 2p3, the so called Gray graph of order 54. In this paper, it is shown that there is no connected cubic semisymmetric graph of order 4p^3 and that there exists a unique cubic semisymmetric graph of order 8p3, which is a Z2 × Z2-covering of the Gray graph.
基金Supported by the National Natural Science Foundation of China(Nos.11301159,11671030,11601132,11501176)the Education Department of Henan Science and Technology Research Key Project(No.13A110543)
文摘A regular edge-transitive graph is said to be semisymmetric if it is not vertex-transitive.Let p be a prime.By Folkman[J.Combin.Theory 3(1967),215–232],there is no cubic semisymmetric graph of order 2p or 2p^2,and by Hua et al.[Science in China A 54(2011),1937–1949],there is no cubic semisymmetric graph of order 4p^2.Lu et al.[Science in China A 47(2004),11–17]classified connected cubic semisymmetric graphs of order 6p^2.In this paper,for p>q≥5 two distinct odd primes,it is shown that the sufficient and necessary conditions which a connected cubic edge transitive bipartite graph of order 2qp^2 is semisymmetric.
基金supported by National Natural Science Foundation of China(Grant Nos.11271267 and 11371204)
文摘Let Γ be a connected regular bipartite graph of order 18 p, where p is a prime. Assume that Γ admits a group acting primitively on one of the bipartition subsets of Γ. Then, in this paper, it is shown that eitherΓ is arc-transitive, or Γ is isomorphic to one of 17 semisymmetric graphs which are constructed from primitive groups of degree 9p.
基金supported by the Fundamental Research Funds for the Central Universities(2020YJS190)the National Natural Science Foundation of China(12071023,11671030)。
文摘Let p be a prime.In this paper,a complete classification of edge-transitive N-covers of a cubic symmetric graph of order 2p is given for the case when N is a twogenerator 2-group whose derived subgroup is either isomorphic to Z_(2)^(3)or generated by at most two elements.As an application,it is shown that 11 is the smallest value of n for which there exist infinitely many cubic semisymmetric graphs with order of the form 2^(n)p.
文摘A graph F is called G-locally-quasiprimitive if each normal subgroup of Gv acts on F（v） trivially or transitively for every vertex v. In this paper we analyse the global action and the structural information of such groups G, extending the previous results for locally-primitive graphs and vertex-transitive locally-quasiprimitive graphs.
