Browsing by Author "Fiol Mora, Miquel Àngel"

Abelian Cayley digraphs with asymptotically large order for any given degree
Aguiló Gost, Francisco de Asis L.; Fiol Mora, Miquel Àngel; Pérez Mansilla, Sonia (20160429)
Article
Open AccessAbelian Cayley digraphs can be constructed by using a generalization to Z(n) of the concept of congruence in Z. Here we use this approach to present a family of such digraphs, which, for every fixed value of the degree, ... 
A Boolean algebra approach to the construction of snarks
Fiol Mora, Miquel Àngel (John Wiley & Sons, 1991)
Part of book or chapter of book
Open AccessThis work deals with the construction of snarks, that is, cubic graphs that cannot be 3edgecolored. A natural generalization of the concept of "color", that describes in a simple way the coloring ("0" or "1") of any set ... 
A differential approach for bounding the index of graphs under perturbations
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (20110902)
Article
Open AccessThis 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 (201103)
External research report
Open Access 
A discrete optimization problem in local networks and data alignment
Fiol Mora, Miquel Àngel; Andrés Yebra, José Luis; Alegre de Miguel, Ignacio; Valero Cortés, Mateo (198706)
Article
Restricted access  publisher's policyThis paper presents the solution of the following optimization problem that appears in the design of doubleloop structures for local networks and also in data memory, allocation and data alignment in SIMD processors. Consider ... 
A geometric approach to dense Cayley digraphs of finite Abelian groups
Aguiló Gost, Francisco de Asis L.; Fiol Mora, Miquel Àngel; Pérez Mansilla, Sonia (2016)
Article
Open AccessWe give a method for constructing infinite families of dense (or eventually likely dense) Cayley digraphs of finite Abelian groups. The diameter of the digraphs is obtained by means of the related minimum distance diagrams. ... 
A geometric approach to dense Cayley digraphs of finite Abelian groups
Aguiló Gost, Francisco de Asis L.; Fiol Mora, Miquel Àngel; Pérez Mansilla, Sonia (Elsevier, 2016)
Conference report
Open AccessWe give a method for constructing infinite families of dense (or eventually likely dense) Cayley digraphs of finite Abelian groups. The diameter of the digraphs is obtained by means of the related {\em minimum distance ... 
Algebraic characterizations of bipartite distanceregular graphs
Fiol Mora, Miquel Àngel (Iniciativa Digital Politècnica, 2011)
Conference report
Open AccessBipartite graphs are combinatorial objects bearing some interesting symmetries. Thus, their spectra—eigenvalues of its adjacency matrix—are symmetric about zero, as the corresponding eigenvectors come into pairs. Moreover, ... 
Algebraic characterizations of distanceregular graphs
Fiol Mora, Miquel Àngel (Elsevier, 2002)
Article
Open AccessWe survey some old and some new characterizations of distanceregular graphs, which depend on information retrieved from their adjacency matrix. In particular, it is shown that a regular graph with d+1 distinct eigenvalues ... 
Algebraic Characterizations of Regularity Properties in Bipartite Graphs
Abiad Monge, Aida; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (2013)
Article
Restricted access  publisher's policyRegular and distanceregular characterizations of general graphs are wellknown. In particular, the spectral excess theorem states that a connected graph GG is distanceregular if and only if its spectral excess (a number ... 
Algunos grafos compuestos
Fiol Mora, Miquel Àngel; Fàbrega Canudas, José (Universidad de Barcelona, Departamento de Estadística Matemática;Universidad Politécnica de Barcelona, Escuela Técnica Superior de Arquitectura, Departamento de Matemáticas y Estadística, 1983)
Article
Open AccessFrom two graphs $G_1$ and $G_2$ on $N_1$ and $N_2$ vertices respectively, the compound graph $G_1[G_2]$ on $N_1N_2$ vertices is obtained connecting $N_2$ copies of $G_1$ following the structure of $G_2$. We present in ... 
A mathematical model for dynamic memory networks
Fàbrega Canudas, José; Fiol Mora, Miquel Àngel; Serra Albó, Oriol; Andrés Yebra, José Luis (Iniciativa Digital Politècnica, 2011)
Conference report
Open AccessThe aim of this paper is to bring together the work done several years ago by M.A. Fiol and the other authors to formulate a quite general mathematical model for a kind of permutation networks known as dynamic memories. A ... 
An algebraic approach to lifts of digraphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Miller, Mirka; Ryan, Joe; Siran, Josef (20181207)
Article
Open AccessWe 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 algebraic model for the storage of data in parallel memories
Fiol Mora, Miquel Àngel; Serra Albó, Oriol (Springer, 1989)
Part of book or chapter of book
Open AccessThe use of SIMD computers requires efficient schemes of storage of data in order to have conflictfree acces in parallel computation. In this paper we restate the problem of finding such chemes in an algebraic context. ... 
An eigenvalue characterization of antipodal distanceregular graphs
Fiol Mora, Miquel Àngel (199711)
Article
Open AccessLet $\Gamma$ be a regular (connected) graph with $n$ vertices and $d+1$ distinct eigenvalues. As a main result, it is shown that $\Gamma$ is an $r$antipodal distanceregular graph if and only if the distance graph $\Gamma_d$ ... 
A new approach to gross error detection for GPS networks
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (20190529)
Article
Open AccessWe present a new matrixbased 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 approach to the spectral excess theorem for distanceregular graphs
Fiol Mora, Miquel Àngel; Gago Álvarez, Silvia; Garriga Valle, Ernest (20090401)
Article
Open AccessThe Spectral Excess Theorem provides a quasispectral characterization for a (regular) graph $\Gamma$ with $d+1$ different eigenvalues to be distanceregular graph, in terms of the mean (d1)excess of its vertices.\ The ... 
An improved upper bound for the order of mixed graphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; López Lorenzo, Nacho (201807)
Article
Open AccessA mixed graph G can contain both (undirected) edges and arcs (directed edges). Here we derive an improved Moorelike bound for the maximum number of vertices of a mixed graph with diameter at least three. Moreover, a ... 
An interlacing approach for bounding the sum of Laplacian eigenvalues of graphs
Abiad, Aida; Fiol Mora, Miquel Àngel; Haemers, Willem H.; Perarnau Llobet, Guillem (2014)
Conference report
Open AccessWe apply eigenvalue interlacing techniques for obtaining lower and upper bounds for the sums of Laplacian eigenvalues of graphs, and characterize equality. This leads to generalizations of, and variations on theorems by ... 
A note on the order of iterated line digraphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel (Wiley, 20160727)
Article
Open AccessGiven a digraph G, we propose a new method to find the recurrence equation for the number of vertices n_k of the kiterated line digraph L_k(G), for k>= 0, where L_0(G) = G. We obtain this result by using the minimal polynomial ...