Scielo RSS <![CDATA[Proyecciones (Antofagasta)]]> https://scielo.conicyt.cl/rss.php?pid=0716-091720130004&lang=es vol. 32 num. 4 lang. es <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[<b>A convergence result for unconditional series in</b> L<sup>p</sup>(ì)]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400001&lng=es&nrm=iso&tlng=es We give sufficient conditions for the convergence almost everywhere of the expansion with respect to an unconditional basis for functions in Lp p > 2. This result extends the classical theorem of Menchoff and Rademacher for orthogonal series in L². <![CDATA[<b>Multiplication</b><b> and Composition operators on</b> <b>ω</b><sub>p</sub><b> (</b><b>f )</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400002&lng=es&nrm=iso&tlng=es In this paper we characterize the boundedness, closed range, in-vertibility of the multiplication operators acting on sequence spaces w p(f) defined by a modulus function. We also make an efforts to study some properties of composition operators on these spaces. <![CDATA[<b>On Contra </b>âè<b>-Continuous Functions</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400003&lng=es&nrm=iso&tlng=es In this paper, we introduce and investigate the notion of contra âè-continuous functions by utilizing â-0-closed sets. We obtain fundamental properties of contra âè-continuous functions and discuss the relationships between contra âè-continuity and other related functions. <![CDATA[<b>On the generating matrices of the </b><em><b>Ê</b></em><b>-Fibonacci</b> <b>numbers</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400004&lng=es&nrm=iso&tlng=es In this paper we define some tridiagonal matrices depending of a parameter from which we will find the k-Fibonacci numbers. And from the cofactor matrix of one of these matrices we will prove some formulas for the k-Fibonacci numbers differently to the traditional form. Finally, we will study the eigenvalues of these tridiagonal matrices. <![CDATA[<b>Banach's and Kannan's fixed point results in fuzzy 2-metric spaces</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400005&lng=es&nrm=iso&tlng=es In this paper we establish two common fixed point theorems in fuzzy 2- metric spaces. These theorems are generalizations of the Banach Contraction mapping principle and the Kannan's fixed point theorem respectively in fuzzy 2-metric spaces. <![CDATA[<b>Existence of positive periodic solutions for two types of second-order nonlinear neutral differential equations with variable delay</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400006&lng=es&nrm=iso&tlng=es In this article we study the existence of positive periodic solutions for two types of second-order nonlinear neutral differential equation with variable delay. The main tool employed here is the Krasnosel-skii's fixedpoint theoremdealing withasum of twomappings, one is a contraction and the other is completely continuous. The results obtained here generalize the work of Cheung, Ren and Han [7. <![CDATA[<b>On generalized binomial series and strongly regular graphs</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400007&lng=es&nrm=iso&tlng=es We consider a strongly regular graph, G, and associate a three dimensional Euclidean Jordan algebra, V, to its adjacency matrix A. Then, by considering binomial series of Hadamard powers of the idem-potents of the unique complete system of orthogonal idempotents of V associated to A, we establish feasibility conditions for the existence of strongly regular graphs. <![CDATA[Fixed points and common fixed points theorems in pseudo-ordered sets]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-09172013000400008&lng=es&nrm=iso&tlng=es Under suitable conditions, we establish the existence of the greatest and the least fixed points of monotone maps defined on nonempty pseudo-ordered sets. Also, we prove that the set of all common fixed points of two categories of finite commutative family F of monotone maps f defined on a nonempty complete trellis is also a nonempty complete trellis.