Scielo RSS <![CDATA[Revista de la Unión Matemática Argentina]]> http://www.scielo.org.ar/rss.php?pid=0041-693220070001&lang=es vol. 48 num. 1 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.ar/img/en/fbpelogp.gif http://www.scielo.org.ar <![CDATA[On the characterization of convex functions]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100001&lng=es&nrm=iso&tlng=es A simple characterization of convex functions as indefinite integrals of non-decreasing ones is obtained, using only Riemann integrals. <![CDATA[Non Positively Curved Metric in the Space of Positive Definite Infinite Matrices]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100002&lng=es&nrm=iso&tlng=es We introduce a Riemannian metric with non positive curvature in the (infinite dimensional) manifold <IMG SRC="/img/revistas/ruma/v48n1/1a020x.png" WIDTH=25 HEIGHT=15>of positive invertible operators of a Hilbert space <IMG SRC="/img/revistas/ruma/v48n1/1a021x.png" WIDTH=15 HEIGHT=12>, which are scalar perturbations of Hilbert-Schmidt operators. The (minimal) geodesics and the geodesic distance are computed. It is shown that this metric, which is complete, generalizes the well known non positive metric for positive definite complex matrices. Moreover, these spaces of finite matrices are naturally imbedded in <IMG SRC="/img/revistas/ruma/v48n1/1a022x.png" WIDTH=25 HEIGHT=15>. <![CDATA[Geodesics and Normal Sections on Real Flag Manifolds]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100003&lng=es&nrm=iso&tlng=es In the present paper we study Riemannian and canonical geodesics in a real flag manifold M, considered as curves in the ambient Euclidean space of the natural embedding of M. <![CDATA[Characterisations of Nelson algebras]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100004&lng=es&nrm=iso&tlng=es Nelson algebras arise naturally in algebraic logic as the algebraic models of Nelson's constructive logic with strong negation. This note gives two characterisations of the variety of Nelson algebras up to term equivalence, together with a characterisation of the finite Nelson algebras up to polynomial equivalence. The results answer a question of Blok and Pigozzi and clarify some earlier work of Brignole and Monteiro. <![CDATA[A qualitative uncertainty principle for completely solvable Lie groups]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100005&lng=es&nrm=iso&tlng=es In this paper, we study a qualitative uncertainty principle for completely solvable Lie groups. <![CDATA[Voronovskaya Type Asymptotic Formula For Lupaş-Durrmeyer Operators]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100006&lng=es&nrm=iso&tlng=es In the present paper, we study some direct results in simultaneous approximation for linear combinations of Lupaş-Beta type operators. <![CDATA[The Boltzmann equation with Force Term near the Vacuum]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100007&lng=es&nrm=iso&tlng=es We prove a theorem of existence, uniqueness and positivity of the solution for the Boltzmann equation with force term and initial data near the Vacuum. <![CDATA[Harmonic Functions on the closed cube: an application to Learning Theory]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100008&lng=es&nrm=iso&tlng=es A natural inference mechanism is presented: the Black Box problem is transformed into a Dirichlet problem on the closed cube. Then it is solved in closed polynomial form, together with a Mean-Value Theorem and a Maximum Principle. An algorithm for calculating the solution is suggested. A special feedforward neural net is deducted for each polynomial. <![CDATA[2005/   LV Reunión anual de Comunicaciones Científicas de la Unión Matemática Argentina y XXVIII Reunión de Educación Matemática]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100009&lng=es&nrm=iso&tlng=es A natural inference mechanism is presented: the Black Box problem is transformed into a Dirichlet problem on the closed cube. Then it is solved in closed polynomial form, together with a Mean-Value Theorem and a Maximum Principle. An algorithm for calculating the solution is suggested. A special feedforward neural net is deducted for each polynomial. <![CDATA[2006/   LVI Reunión anual de Comunicaciones Científicas de la Unión Matemática Argentina XXIX Reunión de Educación Matemática]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100010&lng=es&nrm=iso&tlng=es A natural inference mechanism is presented: the Black Box problem is transformed into a Dirichlet problem on the closed cube. Then it is solved in closed polynomial form, together with a Mean-Value Theorem and a Maximum Principle. An algorithm for calculating the solution is suggested. A special feedforward neural net is deducted for each polynomial. <![CDATA[Carlos Segovia Fernández]]> http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0041-69322007000100011&lng=es&nrm=iso&tlng=es A natural inference mechanism is presented: the Black Box problem is transformed into a Dirichlet problem on the closed cube. Then it is solved in closed polynomial form, together with a Mean-Value Theorem and a Maximum Principle. An algorithm for calculating the solution is suggested. A special feedforward neural net is deducted for each polynomial.