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Construction of standard exact sequences of power series spaces

Markus Poppenberg, Dietmar Vogt (1995)

Studia Mathematica

The following result is proved: Let Λ R p ( α ) denote a power series space of infinite or of finite type, and equip Λ R p ( α ) with its canonical fundamental system of norms, R ∈ 0,∞, 1 ≤ p < ∞. Then a tamely exact sequence (⁎) 0 Λ R p ( α ) Λ R p ( α ) Λ R p ( α ) 0 exists iff α is strongly stable, i.e. l i m n α 2 n / α n = 1 , and a linear-tamely exact sequence (*) exists iff α is uniformly stable, i.e. there is A such that l i m s u p n α K n / α n A < for all K. This result extends a theorem of Vogt and Wagner which states that a topologically exact sequence (*) exists iff α is stable, i.e. s u p n α 2 n / α n < .

Density conditions in Fréchet and (DF)-spaces.

Klaus-Dieter. Bierstedt, José Bonet (1989)

Revista Matemática de la Universidad Complutense de Madrid

We survey our main results on the density condition for Fréchet spaces and on the dual density condition for (DF)-spaces (cf. Bierstedt and Bonet (1988)) as well as some recent developments.

Deviation from weak Banach–Saks property for countable direct sums

Andrzej Kryczka (2015)

Annales UMCS, Mathematica

We introduce a seminorm for bounded linear operators between Banach spaces that shows the deviation from the weak Banach-Saks property. We prove that if (Xν) is a sequence of Banach spaces and a Banach sequence lattice E has the Banach-Saks property, then the deviation from the weak Banach-Saks property of an operator of a certain class between direct sums E(Xν) is equal to the supremum of such deviations attained on the coordinates Xν. This is a quantitative version for operators of the result...

Diametral dimension of some pseudoconvex multiscale spaces

Jean-Marie Aubry, Françoise Bastin (2010)

Studia Mathematica

Stemming from the study of signals via wavelet coefficients, the spaces S ν are complete metrizable and separable topological vector spaces, parametrized by a function ν, whose elements are sequences indexed by a binary tree. Several papers were devoted to their basic topology; recently it was also shown that depending on ν, S ν may be locally convex, locally p-convex for some p > 0, or not at all, but under a minor condition these spaces are always pseudoconvex. We deal with some more sophisticated...

Dichotomies pour les espaces de suites réelles

Pierre Casevitz (2000)

Fundamenta Mathematicae

There is a general conjecture, the dichotomy (C) about Borel equivalence relations E: (i) E is Borel reducible to the equivalence relation E G X where X is a Polish space, and a Polish group acting continuously on X; or (ii) a canonical relation E 1 is Borel reducible to E. (C) is only proved for special cases as in [So].  In this paper we make a contribution to the study of (C): a stronger conjecture is true for hereditary subspaces of the Polish space ω of real sequences, i.e., subspaces such that [ y = ( y n ) n X ...

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