Norms in product spaces which preserve approximation properties.
Functional characterization of best and good approximation in normed product spaces.
In [6], C. Dierick deals with a small but important collection of norms in the product of a finite number of normed linear spaces and he extends to such products some results on functional characterization of best approximations. In this paper we establish the widest scope in which the mentioned results remain valid.
Directional uniform rotundity in spaces of essentially bounded functions.
Smith's counterexample about uniform rotundity in every direction.
It is an open question when the direct sum of normed spaces inherits uniform rotundity in every direction from the factor spaces. M. Smith [4] showed that, in general, the answer is negative. The purpose of this paper is to carry out a complete study of Smith's counterexample.
Relative rotundity in Lp(X).
Continuity of the uniform rotundity modulus relative to linear subspaces
We prove the continuity of the rotundity modulus relative to linear subspaces of normed spaces. As a consequence we reduce the study of uniform rotundity relative to linear subspaces to the study of the same property relative to closed linear subspaces of Banach spaces.
On normal CR-submanifolds of S-manifolds
Many authors have studied the geometry of submanifolds of Kaehlerian and Sasakian manifolds. On the other hand, David E. Blair has initiated the study of S-manifolds, which reduce, in particular cases, to Sasakian manifolds ([1, 2]). I. Mihai ([8]) and L. Ornea ([9]) have investigated CR-submanifolds of S-manifolds. The purpose of the present paper is to study a special kind of such submanifolds, namely the normal CR-submanifolds. In Sections 1 and 2, we review basic formulas and definitions for...
On the Chebyshev alternation theorem.
Rth order Markov models based in multiple logistic regression for covariate dependence of sequences.
Estimación no paramétrica de la función de distribución.
Sea X una variable aleatoria con función de distribución F(x) y función de densidad f(x) y X1, X2,..., Xn un conjunto de observaciones de la variable que pueden ser dependientes. Se definen dos estimadores no paramétricos generales (uno recursivo y el otro no recursivo) de la función de distribución. Bajo condiciones aceptables se obtiene el sesgo y la varianza y covarianza asintótica de los estimadores definidos. Finalmente...
Consistencia de un estimador no paramétrico, recursivo, de la regresión bajo condiciones generales.
Se define un estimador no paramétrico, recursivo, de la función de regresión r(x) = E(Y/X = x), que se calcula a partir de un conjunto de n observaciones {(X1,Yi): i = 1, ..., n} del vector aleatorio (X,Y). Bajo la hipótesis de que los datos son idénticamente distribuidos pero no necesariamente independientes, lo que permite utilizar el estimador definido para estimar la función de autorregresión de una serie de tiempo, se obtienen resultados sobre la consistencia...
Estimación no paramétrica de curvas notables para datos dependientes.
Sea {Xt: t ∈ Z} una serie de tiempo estacionaria, con valores en Rp, verificando la condición de ser α-mixing o L2-estable. A partir de una muestra de tamaño n se define una amplia clase de estimadores no paramétricos de la función de densidad f(x) asociada al proceso, y de la función de autorregresión de orden k: r(y) = E(g(Xt+1)/(Xt-k+1 ... Xt) = y), y ∈ Rk...
A classification of certain submanifolds of an S-manifold
A classification theorem is obtained for submanifolds with parallel second fundamental form of an 𝑆-manifold whose invariant f-sectional curvature is constant.
The set of first-order differential equations with periodic or bounded solutions.
The objective of this note is the announcement of two results of Ambrosetti-Prodi type concerning the existence of periodic (respectively bounded) solutions of the first order differential equation x' = f (t,x).
Suitable norms for simultaneous approximation.
Galois H-objects with a normal basis in closed categories. A cohomological interpretation.
In this paper, for a cocommutative Hopf algebra H in a symmetric closed category C with basic object K, we get an isomorphism between the group of isomorphism classes of Galois H-objects with a normal basis and the second cohomology group H2(H,K) of H with coefficients in K. Using this result, we obtain a direct sum decomposition for the Brauer group of H-module Azumaya monoids with inner action: BMinn(C,H) ≅ B(C) ⊕ H2(H,K) ...
Location of the 2-centers of three points.
On the estimation in a class of diffusion-type processes. Aplication for diffusion branching processes.
In this work a family of stochastic differential equations whose solutions are multidimensional diffusion-type (non necessarily markovian) processes is considered, and the estimation of a parametric vector θ which relates the coefficients is studied. The conditions for the existence of the likelihood function are proved and the estimator is obtained by continuously observing the process. An application for Diffusion Branching Processes is given. This problem has been studied in some special cases...
Smash (co)products and skew pairings.
Let τ be an invertible skew pairing on (B,H) where B and H are Hopf algebras in a symmetric monoidal category C with (co)equalizers. Assume that H is quasitriangular. Then we obtain a new algebra structure such that B is a Hopf algebra in the braided category γD and there exists a Hopf algebra isomorphism w: B ∞ H → B [×] H in C, where B ∞ H is a Hopf algebra with (co)algebra structure the smash (co)product and B [×] H is the Hopf algebra defined by Doi and Takeuchi.
Técnicas de validación cruzada en la estimación de la densidad bajo condiciones de dependencia.
Se estudian modificaciones de las técnicas de validación cruzada de Kullback-Leibler y mínimos cuadrados para obtener el parámetro de suavización asociado a un estimador general no paramétrico de la función de densidad, a partir de la muestra, en el supuesto de que los datos verifican alguna condición débil de dependencia. Se demuestra que los parámetros obtenidos por estas dos técnicas son asintóticamente óptimos. Y se realiza un estudio de simulación.
Page 1 Next