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Projectivity and lifting of Hilbert module maps

Douglas N. Clark (1997)

Annales Polonici Mathematici

In a recent paper, Carlson, Foiaş, Williams and the author proved that isometric Hilbert modules are projective in the category of Hilbert modules similar to contractive ones. In this paper, a simple proof, based on a strengthened lifting theorem, is given. The proof also applies to an equivalent theorem of Foiaş and Williams on similarity to a contraction of a certain 2 × 2 operator matrix.

Rank α operators on the space C(T,X)

Dumitru Popa (2002)

Colloquium Mathematicae

For 0 ≤ α < 1, an operator U ∈ L(X,Y) is called a rank α operator if x τ α x implies Uxₙ → Ux in norm. We give some results on rank α operators, including an interpolation result and a characterization of rank α operators U: C(T,X) → Y in terms of their representing measures.

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