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Porous media: the Muskat problem in 3D
(Mathematical Sciences Publishers, 2013)
The Muskat problem involves filtration of two incompressible fluids throughout a porous medium. In this paper we shall discuss in 3-D the relevance of the RayleighTaylor condition, and the topology of the initial interface, ...
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Algunos espacios topológicos que admiten una medida-categoría
(Universitat de Barcelona, 1984)
Let X be a topological space. A category measure m on X is a countably aditive finite measure defined on the σ-algebra formed by all sets with the Baire property, such that m(E)=0 iff E is of Baire first category. It is ...
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Matemáticas: una ¿triste? historia de amor
(2014-12-25)
Recientemente me encontré en Twitter el vídeo Math tell us three of the saddest love stories del blog Lemongum sobre cómo las matemáticas nos cuentan las historias de amor más tristes. En el presente artículo vamos a ...
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The fixed point property and unbounded sets in CAT(0) spaces
(Elsevier, 2013-12-15)
In this work we study the fixed point property for nonexpansive self-mappings defined on convex and closed subsets of a CAT(0) space. We will show that a positive answer to this problem is very much linked with the Euclidean ...
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Extended eigenvalues of composition operators
(Elsevier, 2021-12-15)
A complex scalar λ is said to be an extended eigenvalue of a bounded linear operator A on a complex Hilbert space if there is a nonzero operator X such that AX=λXA. The results in this paper provide a full solution to the ...
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A note on an ergodic theorem in weakly uniformly convex geodesic spaces
(Springer, 2015-11)
Karlsson and Margulis [A. Karlsson, G. Margulis, A multiplicative ergodic theorem and nonpositively curved spaces. Commun. Math. Phys. 208 (1999), 107-123] proved in the setting of uniformly convex geodesic spaces, which ...
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Funciones con derivadas sucesivas grandes y pequeñas por doquier
(Universitat de Barcelona, 1987)
In this paper we show that, given two double sequences of positive real numbers, α and β, the subset of all functions defined on an open real set which have big derivatives and small ones with respect to α and β, at every ...
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Hardy-Littlewood inequalities for norms of positive operators on sequence spaces
(Elsevier, 2013-01-01)
We consider estimates of Hardy and Littlewood for norms of operators on sequence spaces, and we apply a factorization result of Maurey to obtain improved estimates and simplified proofs for the special case of a positive operator.
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Some examples of matrix-valued orthogonal functions having a differential and an integral operator as eigenfunctions
(Elsevier, 2011-05)
The aim of this paper is to show some examples of matrix-valued orthogonal functions on the real line which are simultaneously eigenfunctions of a second-order differential operator of Schrödinger type and an integral ...
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Universal matrix transforms of holomorphic functions
(University of Houston, 2006)
The phenomenon of overconvergence is related with the convergence of subsequences of the sequence of partial sums of Taylor series at points outside their disk of convergence. During the seventies Chui and Parnes and the ...