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The Zahorski theorem is valid in Gevrey classes

Jean SchmetsManuel Valdivia — 1996

Fundamenta Mathematicae

Let Ω,F,G be a partition of n such that Ω is open, F is F σ and of the first category, and G is G δ . We prove that, for every γ ∈ ]1,∞[, there is an element of the Gevrey class Γγ which is analytic on Ω, has F as its set of defect points and has G as its set of divergence points.

Extension maps in ultradifferentiable and ultraholomorphic function spaces

Jean SchmetsManuel Valdivia — 2000

Studia Mathematica

The problem of the existence of extension maps from 0 to ℝ in the setting of the classical ultradifferentiable function spaces has been solved by Petzsche [9] by proving a generalization of the Borel and Mityagin theorems for C -spaces. We get a Ritt type improvement, i.e. from 0 to sectors of the Riemann surface of the function log for spaces of ultraholomorphic functions, by first establishing a generalization to some nonclassical ultradifferentiable function spaces.

On nuclear maps between spaces of ultradiferentiables jets of Roumieu type.

Jean SchmetsManuel Valdivia — 2003

RACSAM

Si K es un compacto no vacío en R, damos una condición suficiente para que la inyección canónica de ε(K) en ε(K) sea nuclear. Consideramos el caso mixto y obtenemos la existencia de un operador de extensión nuclear de ε(F) en ε(R) donde F es un subconjunto cerrado propio de R y A y D son discos de Banach adecuados. Finalmente aplicamos este último resultado al caso Borel, es decir cuando F = {0}.

Holomorphic extension maps for spaces of Whitney jets.

Jean SchmetsManuel Valdivia — 2001

RACSAM

The key result (Theorem 1) provides the existence of a holomorphic approximation map for some space of C-functions on an open subset of R. This leads to results about the existence of a continuous linear extension map from the space of the Whitney jets on a closed subset F of R into a space of holomorphic functions on an open subset D of C such that D ∩ R = RF.

Explicit extension maps in intersections of non-quasi-analytic classes

Jean SchmetsManuel Valdivia — 2005

Annales Polonici Mathematici

We deal with projective limits of classes of functions and prove that: (a) the Chebyshev polynomials constitute an absolute Schauder basis of the nuclear Fréchet spaces ( ) ( [ - 1 , 1 ] r ) ; (b) there is no continuous linear extension map from Λ ( ) ( r ) into ( ) ( r ) ; (c) under some additional assumption on , there is an explicit extension map from ( ) ( [ - 1 , 1 ] r ) into ( ) ( [ - 2 , 2 ] r ) by use of a modification of the Chebyshev polynomials. These results extend the corresponding ones obtained by Beaugendre in [1] and [2].

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