Exploració per autor "Dalfó Simó, Cristina"
Ara es mostren els items 1-20 de 94
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A differential approach for bounding the index of graphs under perturbations
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2011-09-02)
Article
Accés obertThis paper presents bounds for the variation of the spectral radius (G) of a graph G after some perturbations or local vertex/edge modifications of G. The perturbations considered here are the connection of a new vertex ... -
A differential approach for bounding the index of graphs under perturbations
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2011-03)
Report de recerca
Accés obert -
A general method to find the spectrum and eigenspaces of the k-token graph of a cycle, and 2-token through continuous fractions
Reyes Quiróz, Mónica Andrea; Dalfó Simó, Cristina; Messegué Buisan, Arnau; Fiol Mora, Miquel Àngel (Elsevier, 2025-01)
Article
Accés obertThe k-token graph Fk(G) of a graph G is the graph whose vertices are the k-subsets of vertices from G, two of which being adjacent whenever their symmetric difference is a pair of adjacent vertices in G. In this paper, we ... -
A general method to obtain the spectrum and local spectra of a graph from its regular partitions
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2020-07-12)
Article
Accés obertIt is well known that, in general, part of the spectrum of a graph can be obtained from the adjacency matrix of its quotient graph given by a regular partition. In this paper, a method that gives all the spectrum, and also ... -
A new approach to gross error detection for GPS networks
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2019-05-29)
Article
Accés obertWe present a new matrix-based approach to detect and correct gross errors in GPS geodetic control networks. The study is carried out by introducing a new matrix, whose entries are powers of a (real or complex) variable, ... -
A new general family of mixed graphs
Dalfó Simó, Cristina (2019-01-11)
Article
Accés obertA new general family of mixed graphs is presented, which generalizes both the pancake graphs and the cycle prefix digraphs. The obtained graphs are vertex transitive and, for some values of the parameters, they constitute ... -
A note on a new general family of deterministic hierarchical networks
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2019-06-01)
Article
Accés obertHierarchical network; Small-word; Scale-free; Routing algorithm; Diameter; Clustering -
A note on the order of iterated line digraphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (Wiley, 2016-07-27)
Article
Accés obertGiven a digraph G, we propose a new method to find the recurrence equation for the number of vertices n_k of the k-iterated line digraph L_k(G), for k>= 0, where L_0(G) = G. We obtain this result by using the minimal polynomial ... -
A survey on the missing Moore graph
Dalfó Simó, Cristina (Elsevier, 2019)
Article
Accés obertThis is a survey on some known properties of the possible Moore graph (or graphs) ¿ with degree 57 and diameter 2. Moreover, we give some new results about it, such as the following. When we consider the distance partition ... -
Algebraic Characterizations of Regularity Properties in Bipartite Graphs
Abiad Monge, Aida; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2013)
Article
Accés restringit per política de l'editorialRegular and distance-regular characterizations of general graphs are well-known. In particular, the spectral excess theorem states that a connected graph GG is distance-regular if and only if its spectral excess (a number ... -
Almost Moore and the largest mixed graphs of diameters two and three
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López Lorenzo, Nacho (Elsevier, 2024-01-01)
Article
Accés obertAlmost Moore mixed graphs appear in the context of the degree/diameter problem as a class of extremal mixed graphs, in the sense that their order is one unit less than the Moore bound for such graphs. The problem of their ... -
An algebraic approach to lifts of digraphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Miller, Mirka; Ryan, Joe; Siran, Josef (2019-09)
Article
Accés obertWe study the relationship between two key concepts in the theory of (di)graphs: the quotient digraph, and the lift Ga of a base (voltage) digraph. These techniques contract or expand a given digraph in order to study its ... -
An improved Moore bound and some new optimal families of mixed Abelian Cayley graphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López Lorenzo, Nacho; Ryan, Joe (2020-10)
Article
Accés obertWe consider the case in which mixed graphs (with both directed and undirected edges) are Cayley graphs of Abelian groups. In this case, some Moore bounds were derived for the maximum number of vertices that such graphs can ... -
An improved upper bound for the order of mixed graphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López Lorenzo, Nacho (2018-07)
Article
Accés obertA mixed graph G can contain both (undirected) edges and arcs (directed edges). Here we derive an improved Moore-like bound for the maximum number of vertices of a mixed graph with diameter at least three. Moreover, a ... -
Bipartite biregular Moore graphs
Araujo Pardo, Gabriela; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López Lorenzo, Nacho (2021-11)
Article
Accés obertA 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 ... -
Characterizing (l,m)-walk-regularity
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2009-05)
Article
Accés obertA graph $\G$ with diameter $D$ and $d+1$ distinct eigenvalues is said to be {\it $(\ell,m)$-walk-regular}, for some integers $\ell\in[0,d]$ and $m\in[0,D]$, $\ell\ge m$, if the number of walks of length $i\in [0,\ell]$ ... -
Characterizing identifying codes from the spectrum of a graph or digraph
Balbuena Martínez, Maria Camino Teófila; Dalfó Simó, Cristina; Martínez Barona, Berenice (Elsevier, 2019-06-01)
Article
Accés obertA -identifying code in digraph D is a dominating subset C of vertices of D, such that all distinct subsets of vertices of D with cardinality at most l have distinct closed in-neighborhoods within C. As far as we know, it ... -
Characterizing identifying codes through the spectrum of a graph or digraph
Balbuena Martínez, Maria Camino Teófila; Dalfó Simó, Cristina; Martínez Barona, Berenice (2017)
Text en actes de congrés
Accés obert -
Corrigendum to "Algebraic characterizations of regularity properties in bipartite graphs" Eur. J. Combin. 34 (2013) 1223-1231
Abiad Monge, Aida; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2014)
Article
Accés obert -
Cospectral digraphs from locally line digraphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (Elsevier, 2016-07-01)
Article
Accés obertA digraph Gamma = (V, E) is a line digraph when every pair of vertices u, v is an element of V have either equal or disjoint in -neighborhoods. When this condition only applies for vertices in a given subset (with at least ...