Revistas académicas de la Universidad Católica del Norte
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Eigenvalue localization for complex matrices
No full textIn this paper, we prove that all the eigenvalues ?i of a complex matrix A of order n lie in a disk with center at trA/n and radius
This radius can be bounded without knowing the eigenvalues of A
Bifurcaciones de un oscilador no lineal de tipo cubico, débilmente forzado con fricción cuartica
No full textEn este trabajo se considera el oscilador no lineal débilmente forzado:?+ ?ƒ(x) ? + g(x) = ? cos ?t.donde ƒ(x) es un polinomio de grado cuatro y g(x) es un polinomio cúbico. Se presentan los diagramas de bifurcación en el caso no forzado (? = 0), en función de los coeficientes de ƒ y g.Aplicando el método del promedio (en la versión de P. Holmes y J. Guckenheimer) se obtiene la ecuación promediada asociada, para ?, ? pequeños y la no linealidad cúbica de g(x), también pequeña. Se estudian estas familias y se describen los diferentes retratos de fase que ocurren genéricamente para los coeficientes de ƒ(x)
Un survol sur la théorie de Hodge-de Rham des variétés lisses et singulières
No full textL 'objet de ce papier est de faire un léger survol sur la cohomologie des formes différentielles : de de Rham et sa représentation par les formes harmoniques dans le cas compact lisse, des formes L2 dans le cas singulier et enfin les formes basiques et leur théorie de Hodge pour le cas d 'un feuilletage riemannien sur une variété compacte. 
Local stability results on a model for typhoid fever with a core group
No full textA SIRS epidemiological model with two subpopulation and vital dynamics is analized. Both subpopulations are considered constant by assuming that the birth and the death rate are equal. We analize the case where one subpopulation is a core, that is, a very infectious small group, responsible for a big fraction of the incidence. For this case a threshold is determined and the corresponding equilibrium points for the four dimensional system are shown to be locally stable by means of the classical Liapunov theorem. This system models the dynamics of typhoid fever, where the core is the group of food manipulators. Computer simulation are used to estimate the effect of vaccination on the population
Homotopa de T-algebras de rango 3
No full textEn este artículo caracterizamos los idempotentes de la homótopa de la T-álgebra A = Ke ? U ? V de rango 3 y probamos que si su homótopa también es de rango 3, entonces A = Ke ? V
Saddle connections in parabolic differential equations
No full textWe assume the existence of a saddle connection between two hyperbolic equilibrium points. Necessary and sufficient conditzons are given for the existence of a connection for the perturbed equations. These connections are obtained from the zeros of a finite number of bifurcation functions
A Commutator rigidity for kleinian groups
No full textIn these notes we present a particular rigidity property for finitely generated discrete groups of isometries of the hyperbolic three space H3 . This property is closely related to the following result obtained in the papers [5], [2], [3] and [4]
Introduction a la theorie d'equisingularite pour les formes de Pfaff
No full textDans ce travail, dont une version condensée et sans démonstrations a déja été publiée au C.R.A.S. (cf. [5]), nous nous proposons d'une part d 'établir un lemme d'isotopie pour les germes de formes de Pfaff intégrables, analogue dans un sens que nous préciserons ultérieurement au deuxieme lemme d'isotopie de R. Thom pour les germes de fonctions; d'autre part, nous généralisons aux germes de formes de Pfaff la notion de nombre de J. Milnor d'un germe de fonction. Nous donnons ensuite le lien entre l'invariance de la multiplicité d'intersection, l'invariance du type topologique, la trivialité topologique et les conditions d'incidenses a la Whitney que nous allons définir ci-desous et qui généraliseront aux germes de formes de Pfaff la condition (a¡) de R. Thom et la condition (e) d'équisingularité de B. Teissier bien connues pour les germes de fonctions
Maximal semigroups in finitely generated nilpotent groups
No full textWe obtain a classification of maximal subsemigroups of finitely generated nilpotent groups. In the principal results of this paper we show that there is a one-to-one correspondence between these subsemigroups and the non trivial homomorphisms of the group in R
The dual bade theorem in locally convex spaces and reflexivity of a closed unital subalgebra
No full textThe results presented in this paper extend a dual version of the reflexivity theorem of W. Bade to locally convex spaces. Dual versión of the Bade theorem in a Banach C(K)-module was firstly discovered in [1]. It is our aim to extend it to a locally convex C(K)-module. As a consequence, it is proven that each unital w* operator topology closed subalgebra of the w* operator topology closed algebra generated by a Boolean algebra of projections is reflexive