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Problems concerning n -weak amenability of a Banach algebra

Alireza Medghalchi, Taher Yazdanpanah (2005)

Czechoslovak Mathematical Journal

In this paper we extend the notion of n -weak amenability of a Banach algebra 𝒜 when n . Technical calculations show that when 𝒜 is Arens regular or an ideal in 𝒜 * * , then 𝒜 * is an 𝒜 ( 2 n ) -module and this idea leads to a number of interesting results on Banach algebras. We then extend the concept of n -weak amenability to n .

Projective covers of finitely generated Banach modules and the structure of some Banach algebras.

Oleg Yu. Aristov (2006)

Extracta Mathematicae

The investigation of the structure of biprojective Banach algebras with non-trivial radical [3] forces the author to suppose that the idea of projective cover, which is important in Ring Theory, can be effectively applied to Banach algebras and modules. But, in fact, the structural results on biprojectivity can be easier obtained without projective covers, so there are no references to this matter in [3]. Projective covers of Banach modules are considered in the present article. Except some assertions...

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.

Properties of derivations on some convolution algebras

Thomas Pedersen (2014)

Open Mathematics

For all convolution algebras L 1[0, 1); L loc1 and A(ω) = ∩n L 1(ωn), the derivations are of the form D μ f = Xf * μ for suitable measures μ, where (Xf)(t) = tf(t). We describe the (weakly) compact as well as the (weakly) Montel derivations on these algebras in terms of properties of the measure μ. Moreover, for all these algebras we show that the extension of D μ to a natural dual space is weak-star continuous.

Pseudo-amenability of Brandt semigroup algebras

Maysam Maysami Sadr (2009)

Commentationes Mathematicae Universitatis Carolinae

In this paper it is shown that for a Brandt semigroup S over a group G with an arbitrary index set I , if G is amenable, then the Banach semigroup algebra 1 ( S ) is pseudo-amenable.

Pure states on Jordan algebras

Jan Hamhalter (2001)

Mathematica Bohemica

We prove that a pure state on a C * -algebras or a JB algebra is a unique extension of some pure state on a singly generated subalgebra if and only if its left kernel has a countable approximative unit. In particular, any pure state on a separable JB algebra is uniquely determined by some singly generated subalgebra. By contrast, only normal pure states on JBW algebras are determined by singly generated subalgebras, which provides a new characterization of normal pure states. As an application we contribute...

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