Browsing Morris, Joy by Issue Date

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  • Toida's conjecture is true 
    Dobson, Edward; Morris, Joy (Electronic Journal of CombinatoricsArts and ScienceDepartment of Mathematics and Computer ScienceMississippi State UniversityUniversity of Lethbridge, 2002)
    Let S be a subset of the units in Zn. Let Γ be a circulant graph of order n (a Cayley graph of Zn) such that if ij ∈ E(Γ), then i − j (mod n) ∈ S. Toida conjectured that if Γ0 is another circulant graph of order n, then Γ ...
  • Automorphism groups of wreath product digraphs 
    Dobson, Edward; Morris, Joy (Electronic Journal of CombinatoricsArts and ScienceDepartment of Mathematics and Computer ScienceMississippi State UniversityUniversity of Lethbridge, 2009)
    We generalize a classical result of Sabidussi that was improved by Hemminger, to the case of directed color graphs. The original results give a necessary and sufficient condition on two graphs, C and D, for the automorphsim ...
  • Strongly regular edge-transitive graphs 
    Morris, Joy; Praeger, Cheryl E.; Spiga, Pablo (Drustvo Matematikov, Fizikov in AstronomovArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of LethbridgeUniversity of Western AustraliaUniversity of Padova, 2009)
    In this paper, we examine the structure of vertex- and edge-transitive strongly regular graphs,using normal quotient reduction. We show that their reducible graphs in this family have quasi primitive automorphism groups, ...
  • Hamiltonian cycles in Caley graphs whose order has few prime factors 
    Kutnar, Klavdija; Marusic, Dragan; Morris, Dave Witte; Morris, Joy; Sparl, Primoz (Drustvo Matematikov, Fizikov in AstronomovArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of PrimorskaUniversity of LjubljanaUniversity of Lethbridge, 2012)
    We prove that if Cay(G;S) is a connected Cayley graph with n vertices,and the prime factorization of n is very small, then Cay(G;S) has a hamiltonian cycle. More precisely, if p, q, and r are distinct primes, then n can ...
  • Caley graphs of order 16p are hamiltonian 
    Curran, Stephen J.; Morris, Dave Witte; Morris, Joy (Drustvo Matematikov, Fizikov in AstronomovArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of Pittsburgh at JohnstownUniversity of Lethbridge, 2012)
    Suppose G is a finite group, such that |G| = 16p, where p is prime. We show that if S is any generating set of G, then there is a hamiltonian cycle in the corresponding Cayley graph Cay(G;S).
  • Semiregular automorphisms of cubic vertex-transitive graphs and the abelian normal quotient method 
    Morris, Joy; Spiga, Pablo; Verret, Gabriel (Electronic Journal of CombinatoricsArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of LethbridgeUniversity of Milano-BicoccaThe University of Western Australia, 2015)
    We characterise connected cubic graphs admitting a vertex-transitive group of automorphisms with an abelian normal subgroup that is not semiregular. We illustrate the utility of this result by using it to prove that the ...
  • The CI problem for infinite groups 
    Morris, Joy (Electronic Journal of CombinatoricsArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of Lethbridge, 2016)
    A finite group G is a DCI-group if, whenever S and S0 are subsets of G with the Cayley graphs Cay(G,S) and Cay(G,S0) isomorphic, there exists an automorphism ϕ of G with ϕ(S) = S0. It is a CI-group if this condition holds ...
  • Automorphisms of circulants that respect partitions 
    Morris, Joy (University of Calgary, Department of Mathematics & StatisticsArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of Lethbridge, 2016)
    In this paper, we begin by partitioning the edge (or arc) set of a circulant (di)graph according to which generator in the connection set leads to each edge. We then further refine the partition by subdividing any part that ...
  • On colour-preserving automorphisms of Caley graphs 
    Hujdurovic, Ademir; Kutnar, Klavdija; Morris, Dave Witte; Morris, Joy (Drustvo Matematikov, Fizikov in AstronomovArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of PrimorskaUniversity of Lethbridge, 2016)
    We study the automorphisms of a Cayley graph that preserve its natural edge-colouring. More precisely, we are interested in groups G, such that every such automorphism of every connected Cayley graph on G has a very simple ...
  • Cyclic m-cycle systems of complete graphs minus a 1-factor 
    Jordan, Heather; Morris, Joy (The University of Queensland, Centre for Discrete Mathematics and ComputingArts and ScienceDepartment of Mathematics and Computer ScienceAlbion CollegeUniversity of Lethbridge, 2017)
    In this paper, we provide necessary and sufficient conditions for the existence of a cyclic m-cycle system of Kn −I when m and n are even and m | n.
  • Vertex-transitive digraphs with extra automorphisms that preserve the natural arc-colouring 
    Dobson, Ted; Hujdurovic, Ademir; Kutnar, Klavdija; Morris, Joy (The University of Queensland, Centre for Discrete Mathematics and ComputingArts and ScienceDepartment of Mathematics and Computer ScienceMississippi State UniversityUniversity of PrimoskaUniversity of Lethbridge, 2017)
    In a Cayley digraph on a group G, if a distinct colour is assigned to each arc-orbit under the left-regular action of G, it is not hard to show that the elements of the left-regular action of G are the only digraph ...
  • Characterising CCA Sylow cyclic groups whose order is not divisible by four 
    Morgan, Luke; Morris, Joy; Verret, Gabriel (Drustvo Matematikov, Fizikov in AstronomovArts and ScienceDepartment of Mathematics and Computer ScienceUniversity of Western AustraliaUniversity of Lethbridge, 2018)
    A Cayley graph on a group G has a natural edge-colouring. We say that such a graph is CCA if every automorphism of the graph that preserves this edge-colouring is an element of the normaliser of the regular representation ...
  • On the automorphism groups of almost all circulant graphs and digraphs 
    Bhoumik, Soumya; Dobson, Edward; Morris, Joy (Drustvo Matematikov, Fizikov in AstronomovArts and ScienceDepartment of Mathematics and Computer ScienceFort Hays State UniversityMississippi State UniversityUniversity of PrimorskaUniversity of Lethbridge, 2018)
    We attempt to determine the structure of the automorphism group of a generic circulant graph. We first show that almost all circulant graphs have automorphism groups as small as possible. The second author has conjectured ...