Now showing items 13-24 of 222

  • Rainbow spanning subgraphs in bounded edge–colourings of graphs with large minimum degree 

    Cano Vila, María del Pilar; Perarnau Llobet, Guillem; Serra Albó, Oriol (2017-08-01)
    Article
    Open Access
    We study the existence of rainbow perfect matching and rainbow Hamiltonian cycles in edge–colored graphs where every color appears a bounded number of times. We derive asymptotically tight bounds on the minimum degree of ...
  • On sets defining few ordinary planes 

    Ball, Simeon Michael (2017-09-19)
    Article
    Open Access
    Let S be a set of n points in real three-dimensional space, no three collinear and not all co-planar. We prove that if the number of planes incident with exactly three points of S is less than (Formula presented.) for some ...
  • A generalisation of Sylvester's problem to higher dimensions 

    Ball, Simeon Michael; Monserrat, Joaquim (2017-07-01)
    Article
    Open Access
    In this article we consider $S$ to be a set of points in $d$-space with the property that any $d$ points of $S$ span a hyperplane and not all the points of $S$ are contained in a hyperplane. The aim of this article is to ...
  • A finite version of the Kakeya problem 

    Ball, Simeon Michael; Blokhuis, Aart; Domenzain, Diego (2016-06-02)
    Article
    Open Access
    Let L be a set of lines of an affine space over a field and let S be a set of points with the property that every line of L is incident with at least N points of S. Let D be the set of directions of the lines of L considered ...
  • On quotient digraphs and voltage digraphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Miller, Mirka; Ryan, Joe (2017-10)
    Article
    Open Access
    We study the relationship between two key concepts in the theory of digraphs, those of quotient digraphs and voltage digraphs. These techniques contract or expand a given digraph in order to study its characteristics,or ...
  • The spectra of subKautz and cyclic Kautz digraphs 

    Dalfó Simó, Cristina (Elsevier, 2017-10-15)
    Article
    Open Access
    Kautz digraphs K(d,l) are a well-known family of dense digraphs, widely studied as a good model for interconnection networks. Closely related with these, the cyclic Kautz CK(d,l) and the subKautz sK(d,2) digraphs were ...
  • A new labeling construction from the -product 

    López Masip, Susana Clara; Muntaner Batle, Francesc Antoni; Prabu, M. (2017-08-01)
    Article
    Open Access
    The ¿h-product that is referred in the title was introduced in 2008 as a generalization of the Kronecker product of digraphs. Many relations among labelings have been obtained since then, always using as a second factor a ...
  • The number and degree distribution of spanning trees in the Tower of Hanoi graph 

    Zhang, Zhongzhi; Wu, Shunqi; Li, Mingyun; Comellas Padró, Francesc de Paula (2016-01-04)
    Article
    Open Access
    The number of spanning trees of a graph is an important invariant related to topological and dynamic properties of the graph, such as its reliability, communication aspects, synchronization, and so on. However, the practical ...
  • Iterated line digraphs are asymptotically dense 

    Dalfó Simó, Cristina (Elsevier, 2017)
    Article
    Open Access
    We show that the line digraph technique, when iterated, provides dense digraphs, that is, with asymptotically large order for a given diameter (or with small diameter for a given order). This is a well- known result for ...
  • The normalized Laplacian spectrum of subdivisions of a graph 

    Xie, Pinchen; Zhang, Zhongzhi; Comellas Padró, Francesc de Paula (2016-08-05)
    Article
    Open Access
    Determining and analyzing the spectra of graphs is an important and exciting research topic in mathematics science and theoretical computer science. The eigenvalues of the normalized Laplacian of a graph provide information ...
  • On perfect and quasiperfect dominations in graphs 

    Hernando Martín, María del Carmen; Mora Giné, Mercè; Pelayo Melero, Ignacio Manuel; Cáceres, José; Puertas, M. Luz (2017-02-27)
    Article
    Open Access
    A subset S ¿ V in a graph G = ( V , E ) is a k -quasiperfect dominating set (for k = 1) if every vertex not in S is adjacent to at least one and at most k vertices in S . The cardinality of a minimum k -quasiperfect ...
  • Perfect (super) Edge-Magic Crowns 

    López Masip, Susana Clara; Muntaner Batle, Francesc Antoni; Prabu, M. (2017-01-06)
    Article
    Open Access
    A graph G is called edge-magic if there is a bijective function f from the set of vertices and edges to the set {1,2,…,|V(G)|+|E(G)|} such that the sum f(x)+f(xy)+f(y) for any xy in E(G) is constant. Such a function is ...