Invariant vector means and complementability of Banach spaces in their second duals

Autor: Radosław Łukasik
Rok vydání: 2022
Předmět:
Zdroj: Aequationes mathematicae. 96:1041-1052
ISSN: 1420-8903
0001-9054
DOI: 10.1007/s00010-022-00866-6
Popis: Let X be a Banach space. Fix a torsion-free commutative and cancellative semigroup S whose torsion-free rank is the same as the density of $$X^{**}$$ X ∗ ∗ . We then show that X is complemented in $$X^{**}$$ X ∗ ∗ if and only if there exists an invariant mean $$M:\ell _\infty (S,X)\rightarrow X$$ M : ℓ ∞ ( S , X ) → X . This improves upon previous results due to Bustos Domecq (J Math Anal Appl 275(2):512–520, 2002), Kania (J Math Anal Appl 445:797–802, 2017), Goucher and Kania (Studia Math 260:91–101, 2021).
Databáze: OpenAIRE
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