Browsing Articles publicats (Matemàtica) by Title
Now showing items 221240 of 266

Small cutsets in arctransitive digraphs of prime degree
(Elsevier, 2013)We give an upper bound for the size of nontrivial sets that have small boundary in a family of arctransitive digraphs. We state the exact size for these sets in case of prime degree. We also give a lower bound for the ... 
Space–time trends in Spanish bird electrocution rates from alternative information sources
(Elsevier, 2015)Interaction with manmade infrastructures is one of the main sources of nonnatural bird mortality. Here, we use a longterm study (1980–2010) to analyse spatial and temporal patterns in avian electrocution in Spain, using ... 
Spatiotemporal configurations of humancaused fires in Spain through point patterns
(MDPI, 2016)Humancaused wildfires are often regarded as unpredictable, but usually occur in patterns aggregated over space and time. We analysed the spatiotemporal configuration of 7790 anthropogenic wildfires (2007–2013) in nine ... 
Spectra and eigenspaces from regular partitions of Cayley (di)graphs of permutation groups
(Elsevier, 2020)In this paper, we present a method to obtain regular (or equitable) partitions of Cayley (di)graphs (that is, graphs, digraphs, or mixed graphs) of permutation groups on n letters. We prove that every partition of the ... 
Spectra and eigenspaces of arbitrary lifts of graphs
(Faculty of Mathematics, Physics and Informatics, Comenius University, 2019)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 (regularor not). 
Strongly formal Weierstrass nonintegrability for polynomial differential systems in C2
(Bolyai Institute, University of SzegedHungarian Academy of Sciences, 2020)Recently a criterion has been given for determining the weakly formal Weierstrass nonintegrability of polynomial differential systems in C2 . Here we extend this criterion for determining the strongly formal Weierstrass ... 
Sufficient conditions for a digraph to admit a (1,≤ℓ)identifying code
(University of Zielona Góra, 2019)A (1, ≤ `)identifying code in a digraph D is a subset C of vertices of D such that all distinct subsets of vertices of cardinality at most ` have distinct closed inneighbourhoods within C. In this paper, we give some ... 
Super edgemagic models
(Springer, 2011)In this paper, we generalize the concept of super edgemagic graph by introducing the new concept of super edgemagic models. 
Synthetic generation of social network data with endorsements
(Palgrave Macmillan, 2014)In many simulation studies involving networks there is the need to rely on a sample network to perform the simulation experiments. In many cases, real network data is not available due to privacy concerns. In that case we ... 
The (∆,D) and (∆,N) problems in doublestep digraphs with unilateral distance
(Indonesian Combinatorial Society (InaCombS); Graph Theory and Applications (GTA) Research Centre; University of Newcastle, Australia; Institut Teknologi Bandung (ITB), Indonesia, 2014)We study the (Delta,D) and (Delta,N) problems for doublestep digraphs considering the unilateral distance, which is the minimum between the distance in the digraph and the distance in its converse digraph, obtained by ... 
The 2adic valuation of the cardinality of Jacobians of genus 2 curves over quadratic towers of finite fields
(World Scientific Publishing, 2018)Given a genus 2 curve C defined over a finite field Fq of odd characteristic such that 2#Jac(C)(Fq), we study the growth of the 2adic valuation of the cardinality of the Jacobian over a tower of quadratic extensions of ... 
The center problem and composition condition for Abel differential equations
(Elsevier, 2015)The classical Poincaré centerfocus problem for planar polynomial systems of ordinary differential equations can be transformed, in certain particular cases, to the center problem of a trigonometric Abel differential ... 
The center problem for a 2:3 resonant cubic Lotka–Volterra system
(Elsevier, 2013)In this paper we obtain conditions on the coefficients of a cubic Lotka–Volterra system of the form equation(1) x=x(2a20x2a11xya02y2), ẏ=y(3+b20x2+b11xy+b02y2), which fulfillment yields the existence in a ... 
The cubic polynomial differential systems with two circles as algebraic limit cycles
(Walter de Gruyter GmbH, 2018)In this paper we characterize all cubic polynomial differential systems in the plane having two circles as invariant algebraic limit cycles. 
The cyclicity of polynomial centers via the reduced bautin depth
(American Mathematical Society, 2016)We describe a method for bounding the cyclicity of the class of monodromic singularities of polyn omial planar families of vector fields X λ with an analytic Poincar e first return map having a polynomial Bautin ideal B ... 
The Degree/Diameter Problem for Mixed Abelian Cayley Graphs
(Elsevier, 20171120)This paper investigates the upper bounds for the number of vertices in mixed abelian Cayley graphs with given degree and diameter. Additionally, in the case when the undirected degree is equal to one, we give a construction ... 
The diameter of cyclic Kautz digraphs
(Faculty of Sciences and Mathematics, University of Nis, Serbia, 2017)We present a new kind of digraphs, called cyclic Kautz digraphs CK(d, ɭ), which are subdigraphs of the wellknown Kautz digraphs K(d,ɭ). The latter have the smallest diameter among all digraphs with their number of ... 
The Hopf cyclicity of the centers of a class of quintic polynomial vector fields
(Elsevier, 20150120)We consider families of planar polynomial vector fields having a singularity with purely imaginary eigenvalues for which a basis of its Bautin ideal B is known. We provide an algorithm for computing an upper bound of the ... 
The inverse integrating factor and the Poincaré map
(American Mathematical Society, 2010)This work is concerned with planar real analytic differential systems with an analytic inverse integrating factor defined in a neighborhood of a regular orbit. We show that the inverse integrating factor defines an ... 
The jumping knight and other (super) edgemagic constructions
(Springer, 2014)Let G be a graph of order p and size q with loops allowed. A bijective function f:V(G)∪E(G)→{i}p+qi=1 is an edgemagic labeling of G if the sum f(u)+f(uv)+f(v)=k is independent of the choice of the edge uv. The constant k ...