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AbstractA ℂ-linear map θ(not necessarily bounded) between two Hilbert C*-modules is said to be ‘orthogonality preserving’ if 〈θ(x),θ(y)〉=0 whenever 〈x,y〉=0. We prove that if θis an orthogonality preserving map from a full Hilbert C0(Ω)-module Einto another Hilbert C0(Ω) -module Fthat satisfies a weaker notion of C0(Ω) -linearity (called ‘localness’), then θis bounded and there exists ϕ∈Cb(Ω)+such that 〈θ(x),θ(y)〉=ϕ⋅〈x,y〉 for all x,y∈E.

Abstract. In this short article, we will give several results concerning closed invariant ideals of crossed products using some “topological arguments”.

Abstract.: We will prove a result concerning the inclusion of non-trivial invariant ideals inside non-trivial ideals of a twisted crossed product. We will also give results concerning the primeness and simplicity of crossed products of twisted actions of locally compact groups on -algebras.

In this paper, we study amenable unitary corepresentations of Kac algebras. We also study some sorts of “noncommutative” Reiter's properties. As an application, we find some new equivalent conditions for the amenability of Kac algebras.

AbstractWe will consider coactions of discrete groups on C*-algebras and imitate some of the results about compact group actions on C*-algebras. In particular, the crossed product of a reduced coaction of a discrete amenable group Gon Ais liminal (respectively, postliminal) if and only if the fixed point algebra of is. Moreover, we will also consider ergodic coactions on C*-algebras.

In this paper, we study coactions and their crossed products by Hopf C*‐algebras defined by multiplicative unitaries. We generalize some results in the case of group actions and coactions. Furthermore, when applied to the group case, some of these generalizations improve the original results. For example, we obtained the following result. Let Abe a C*‐algebra with coaction ɛ by Swhere Sis a Hopf C*‐algebra defined by an amenable multiplicative unitary. If Ais nuclear or C*‐exact, then so is AXɛ, rŜ. This implies that if (A, G, α) is any C*‐dynamical system such that AXα, rGis nuclear or C*‐exact, then so is A.

The high frequency behaviour of monolithic microwave integrated circuits (MMICs) is highly affected by the way in which the package is grounded. The authors investigate, by computer simulation and experiments, the effects of poor grounding and optimal allocation of ground vias on the performance of packaged MMICs.

In this paper, we study coactions and their crossed products by Hopf C*-algebras defined by multiplicative unitaries. We generalize some results in the case of group actions and coactions. Furthermore, when applied to the group case, some of these generalizations improve the original results. For example, we obtained the following result. Let A be a C*-algebra with coaction ɛ by S where S is a Hopf C*-algebra defined by an amenable multiplicative unitary. If A is nuclear or C*-exact, then so is A Xɛ, rŜ. This implies that if (A, G, α) is any C*-dynamical system such that A Xα, rG is nuclear or C*-exact, then so is A.