Articles publicats (Matemàtica)
Browse by
Recent Submissions

New cyclic Kautz digraphs with optimal diameter
(University of Calgary, 20211231)We obtain a new family of digraphs with minimal diameter, that is, given the number of vertices and outdegree, there is no other digraph with a smaller diameter. This new family of digraphs are called `modified cyclic ... 
On the spectra and eigenspaces of the universal adjacency matrices of arbitrary lifts of graphs
(Taylor & Francis, 20220219)The universal adjacency matrix U of a graph Γ, with adjacency matrix A, is a linear combination of A, the diagonal matrix D of vertex degrees, the identity matrix I, and the all1 matrix J with real coefficients, that is, ... 
Center problem with characteristic directions and inverse integrating factors
(Elsevier, 2022)We consider the centerfocus problem for analytic families of planar vector fields having a monodromic singularity with characteristic directions. We give a method to compute the center conditions of the family provided ... 
Invariant Algebraic Curves of Generalized Liénard Polynomial Differential Systems
(MDPI, 2022)In this study, we focus on invariant algebraic curves of generalized Liénard polynomial differential systems x 0 = y, y 0 = −fm(x)y − gn(x), where the degrees of the polynomials f and g are m and n, respectively, and ... 
Full wave analysis of stripping chronopotentiometry at scanned deposition potential (SSCP): obtaining binding curves in labile heterogeneous macromolecular systems for any metaltoligand ratio.
(Elsevier, 2020)The different deposition potentials applied in Scanned Stripping ChronoPotentiometry (SSCP) probe different values of the free metal and complex concentrations at the electrode surface. The knowledge of these concentrations ... 
Analytic integrability around the origin of certain differential system
(Wilmington Scientific Publisher, 2022)In this work we consider the polynomial differential system x˙=−y+xyn−1, y˙=x+ayxn−1, where a∈R and n≥2 with n∈N. This system is a certain generalization of the classical Liénard system. We study the center problem and ... 
Analytic integrability around a nilpotent singularity: The nongeneric case
(American Institute of Mathematical Sciences, 2020)Recently, in [9] is characterized the analytic integrability problem around a nilpotent singularity for differential systems in the plane under generic conditions. In this work we solve the remaining case completing the ... 
Liouvillian integrability of a general RayleighDuffing oscillator
(Atlantis; Taylor & Francis, 2019)We give a complete description of the Darboux and Liouville integrability of a general RayleighDuffing oscillator through the characterization of its polynomial first integrals, Darboux polynomials and exponential factors. 
Integrability Conditions for Complex Homogeneous Kukles Systems
(Atlantis and Taylor & Francis, 2018)In this paper we study the existence of local analytic first integrals for complex polynomial differential systems of the form ẋ = x + Pn(x, y), ẏ = −y, where Pn(x,y) is a homogeneous polynomial of degree n, called the ... 
The center problem for Z_2symmetric nilpotent vector fields
(Elsevier, 2018)We say that a polynomial differential system ˙x = P(x, y), ˙y = Q(x, y) having the origin as a singular point is Z2symmetric if P(−x, −y) = −P(x, y) and Q(−x, −y) = −Q(x, y). It is known that there are nilpotent centers ... 
New constructions for the nqueens problem
(Springer, 202002)Let D be a digraph, possibly with loops. A queen labeling of D is a bijective function l:V(G)⟶{1,2,…,V(G)} such that, for every pair of arcs in E(D), namely (u, v) and (u′,v′) we have (i) l(u)+l(v)≠l(u′)+l(v′) and (ii) ... 
(Di)graph decompositions and magic type labelings: a dual relation
(Springer, 202010)A graph G is called edgemagic 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 ... 
Contrariando o “velho do Restelo”: análise global e componentes das atitudes em relação à estatística em professores Portugueses
(Universidade de Aveiro, 2018)Es necesario conocer las actitudes de los profesores hacia la estadística, en el sentido de entender mejor su predisposición y compromiso hacia el proceso de enseñanzaaprendizaje y su formación. Así, este ... 
Cospectral digraphs from locally line digraphs
(Elsevier, 201607)A digraph Γ =(V, E) is a line digraph when every pair of vertices u, v∈V have either equal or disjoint inneighborhoods. When this condition only applies for vertices in a given subset (with at least two elements), we say ... 
Deterministic hierarchical networks
(IOP Publishing, 201605)It has been shown that many networks associated with complex systems are smallworld (they have both a large local clustering coefficient and a small diameter) and they are also scalefree (the degrees are distributed ... 
The degree/diameter problem in maximal planar bipartite graphs
(Electronic Journal of Combinatorics, 2016)The (∆, D) (degree/diameter) problem consists of finding the largest possiblenumber of verticesnamong all the graphs with maximum degree ∆ and diameter D. We consider the (∆, D) problem for maximal planar bipartite ... 
A note on the order of iterated line digraphs
(Wiley Periodicals Inc., 201606)Given a digraph G, we propose a new method to find therecurrence equation for the number of vertices nk of the kiterated linedigraph Lk(G), for k≥0, where L0(G)=G. We obtain this result by usingthe minimal polynomial of ... 
On quotient digraphs and voltage digraphs
(Combinatorial Mathematics Society of Australasia (CMSA), 2017)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 ... 
From expanded digraphs to lifts of voltage digraphs and line digraphs
(Combinatorial Mathematics Society of Australasia (CMSA), 2017)In this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show the close relationship between lifted digraphs of voltage digraphs ... 
Edge distanceregular graphs
(Elsevier, 201112)Edgedistanceregularity is a concept recently introduced by the authors which is similar to that of distanceregularity, but now the graph is seen from each of its edges instead of from its vertices. More precisely, a ...