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n -inner product spaces and projections

Aleksander Misiak, Alicja Ryż (2000)

Mathematica Bohemica

This paper is a continuation of investigations of n -inner product spaces given in [five, six, seven] and an extension of results given in [three] to arbitrary natural n . It concerns families of projections of a given linear space L onto its n -dimensional subspaces and shows that between these families and n -inner products there exist interesting close relations.

Numerical radius inequalities for Hilbert C * -modules

Sadaf Fakri Moghaddam, Alireza Kamel Mirmostafaee (2022)

Mathematica Bohemica

We present a new method for studying the numerical radius of bounded operators on Hilbert C * -modules. Our method enables us to obtain some new results and generalize some known theorems for bounded operators on Hilbert spaces to bounded adjointable operators on Hilbert C * -module spaces.

On complete-cocomplete subspaces of an inner product space

David Buhagiar, Emmanuel Chetcuti (2005)

Applications of Mathematics

In this note we give a measure-theoretic criterion for the completeness of an inner product space. We show that an inner product space S is complete if and only if there exists a σ -additive state on C ( S ) , the orthomodular poset of complete-cocomplete subspaces of S . We then consider the problem of whether every state on E ( S ) , the class of splitting subspaces of S , can be extended to a Hilbertian state on E ( S ¯ ) ; we show that for the dense hyperplane S (of a separable Hilbert space) constructed by P. Pták and...

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