Recent Submissions

  • Some product graphs with power dominating number at most 2 

    Shahbaznejad, Najibeh; Kazemi, Adel P.; Pelayo Melero, Ignacio Manuel (Elsevier, 2021-07-08)
    Article
    Open Access
    Let S be a set of vertices of a graph G. Let M[S] be the set of vertices built from the closed neighborhood N[S] of S, by iteratively applying the following propagation rule: if a vertex and all but exactly one of its ...
  • On the spectra and eigenspaces of the universal adjacency matrices of arbitrary lifts of graphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Pavlíková, Sona; Siran, Josef (Taylor & Francis, 2022-02-19)
    Article
    Restricted access - publisher's policy
    The universal adjacency matrix U of a graph G, with adjacency matrix A, is a linear combination of A, the diagonal matrix D of vertex degrees, the identity matrix I, and the all-1 matrix J with real coefficients, that is, ...
  • Optimization of eigenvalue bounds for the independence and chromatic number of graph powers 

    Abiad, Aida; Coutinho, Gabriel; Fiol Mora, Miquel Àngel; Nogueira, Bruno; Zeijlemaker, Shanne (2022-03)
    Article
    Open Access
    The k-thpower of a graph G=(V,E), G^k, is the graph whose vertex set is V and in which two distinct vertices are adjacent if and only if their distance in G is at most k. This article proves various eigenvalue bounds for ...
  • On symmetric association schemes and associated quotient-polynomial graphs 

    Fiol Mora, Miquel Àngel; Penjic, Safet (2021-01-01)
    Article
    Open Access
    Let denote an undirected, connected, regular graph with vertex set , adjacency matrix , and distinct eigenvalues. Let denote the subalgebra of generated by . We refer to as the adjacency algebra of . In this paper we ...
  • On the Laplacian spectra of token graphs 

    Dalfó Simó, Cristina; Duque, Frank; Fabila Monroy, Ruy; Fiol Mora, Miquel Àngel; Huemer, Clemens; Trujillo Negrete, Ana Laura; Zaragoza Martínez, Francisco (Elsevier, 2021-09-15)
    Article
    Restricted access - publisher's policy
    We study the Laplacian spectrum of token graphs, also called symmetric powers of graphs. The k-token graph of a graph G is the graph whose vertices are the k-subsets of vertices from G, two of which being adjacent whenever ...
  • New cyclic Kautz digraphs with optimal diameter 

    Böhmová, Katerina; Dalfó Simó, Cristina; Huemer, Clemens (2021)
    Article
    Open Access
    We obtain a new family of digraphs with minimal diameter, that is, given the number of vertices and out-degree, there is no other digraph with a smaller diameter. This new family of digraphs are called `modified cyclic ...
  • Spectra and eigenspaces of arbitrary lifts of graphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Pavlíková, Sona; Siran, Josef (2021-09)
    Article
    Open Access
    We describe, in a very explicit way, a method for determining the spectra and bases of all the corresponding eigenspaces of arbitrary lifts of graphs (regular or not).
  • Trees whose even-degree vertices induce a path are antimagic 

    Lozano Boixadors, Antoni; Mora Giné, Mercè; Seara Ojea, Carlos; Tey Carrera, Joaquín (2022-08)
    Article
    Open Access
    An antimagic labeling of a connected graph G is a bijection from the set of edges E(G) to {1, 2, . . . , |E(G)|} such that all vertex sums are pairwise distinct, where the vertex sum at vertex v is the sum of the labels ...
  • Uniform forcing and immune sets in graphs and hypergraphs 

    Fàbrega Canudas, José; Martí Farré, Jaume; Muñoz López, Francisco Javier (2021-12-31)
    Article
    Restricted access - publisher's policy
    Zero forcing is an iterative coloring process on a graph that has been widely used in such different areas as the modelling of propagation phenomena in networks and the study of minimum rank problems in matrices and graphs. ...
  • Bipartite biregular Moore graphs 

    Araujo Pardo, Gabriela; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López Lorenzo, Nacho (2021-11)
    Article
    Restricted access - publisher's policy
    A bipartite graph G = (V, E) with V = V1 ¿ V2 is biregular if all the vertices of a stable set Vi have the same degree ri for i = 1, 2. In this paper, we give an improved new Moore bound for an infinite family of such ...
  • On d-Fibonacci digraphs 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2021-10-03)
    Article
    Open Access
    The d-Fibonacci digraphs F(d, k), introduced here, have the number of vertices following some generalized Fibonacci-like sequences. They can be defined both as digraphs on alphabets and as iterated line digraphs. Here we ...
  • Decompositions of a rectangle into non-congruent rectangles of equal area 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López Lorenzo, Nacho; Martínez Pérez, Álvaro (2021-06)
    Article
    Restricted access - publisher's policy
    In this paper, we deal with a simple geometric problem: Is it possible to partition a rectangle into k non-congruent rectangles of equal area? This problem is motivated by the so-called ‘Mondrian art problem’ that asks a ...

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