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Contractible quantum Arens-Michael algebras

Nina V. Volosova (2010)

Banach Center Publications

We consider quantum analogues of locally convex spaces in terms of the non-coordinate approach. We introduce the notions of a quantum Arens-Michael algebra and a quantum polynormed module, and also quantum versions of projectivity and contractibility. We prove that a quantum Arens-Michael algebra is contractible if and only if it is completely isomorphic to a Cartesian product of full matrix C*-algebras. Similar results in the framework of traditional (non-quantum) approach are established, at the...

Control on weak asymptotic abelianness with the help of the crossed product construction

Heide Narnhofer (1998)

Banach Center Publications

The crossed product construction is used to control in some examples the asymptotic behaviour of time evolution. How invariant states on a small algebra can be extended to invariant states on a larger algebra reduces to solving an eigenvalue problem. In some cases (the irrational rotation algebra) this eigenvalue problem has only trivial solutions and by reduction of the subalgebra control on all invariant states can be found.

Convolutions related to q-deformed commutativity

Anna Kula (2010)

Banach Center Publications

Two important examples of q-deformed commutativity relations are: aa* - qa*a = 1, studied in particular by M. Bożejko and R. Speicher, and ab = qba, studied by T. H. Koornwinder and S. Majid. The second case includes the q-normality of operators, defined by S. Ôta (aa* = qa*a). These two frameworks give rise to different convolutions. In particular, in the second scheme, G. Carnovale and T. H. Koornwinder studied their q-convolution. In the present paper we consider another convolution of measures...

Covariance algebra of a partial dynamical system

Bartosz Kosma Kwaśniewski (2005)

Open Mathematics

A pair (X, α) is a partial dynamical system if X is a compact topological space and α: Δ→ X is a continuous mapping such that Δ is open. Additionally we assume here that Δ is closed and α(Δ) is open. Such systems arise naturally while dealing with commutative C *-dynamical systems. In this paper we construct and investigate a universal C *-algebra C *(X,α) which agrees with the partial crossed product [10] in the case α is injective, and with the crossed product by a monomorphism [22] in the case...

Covariant version of the Stinespring type theorem for Hilbert C*-modules

Maria Joiţa (2011)

Open Mathematics

In this paper, we prove a covariant version of the Stinespring theorem for Hilbert C*-modules. Also, we show that there is a bijective correspondence between operator valued completely positive maps, (u′, u)-covariant with respect to the dynamical system (G, η, X) on Hilbert C*-modules and (u′, u)-covariant operator valued completely positive maps on the crossed product G ×η X of X by η.

Crossed products by Hilbert pro-C*-bimodules

Maria Joiţa, Ioannis Zarakas (2013)

Studia Mathematica

We define the crossed product of a pro-C*-algebra A by a Hilbert A-A pro-C*-bimodule and we show that it can be realized as an inverse limit of crossed products of C*-algebras by Hilbert C*-bimodules. We also prove that under some conditions the crossed products of two Hilbert pro-C*-bimodules over strongly Morita equivalent pro-C*-algebras are strongly Morita equivalent.

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