On Unitary Convex Decompositions of Vectors in a Jb∗-algebra

Asymmetric Decompositions of Vectors in Jb∗-algebras

By investigating the extent to which variation in the coefficients of a convex combination of unitaries in a unital JB-algebra permits that combination to be expressed as convex combination of fewer unitaries of the same algebra, we generalise various results of R. V. Kadison and G. K. Pedersen. In the sequel, we shall give a couple of characterisations of JB-algebras of tsr

Convex combinations of unitaries in JB∗-algebras

We continue our recent efforts to exploit the notion of a unitary isotope to study convex combinations of unitaries in an arbitrary JB∗-algebra. Exact analogues of C∗-algebraic results, due to R. V. Kadison, C. L. Olsen and G. K. Pedersen, are proved for general JB∗-algebras. We show that if a contraction in a JB∗-algebra is a convex combination of n unitaries, then it is also a mean of n unita...

Multi-Frame Vectors for Unitary Systems in Hilbert $C^{*}$-modules

In this paper, we focus on the structured multi-frame vectors in Hilbert $C^*$-modules. More precisely, it will be shown that the set of all complete multi-frame vectors for a unitary system can be parameterized by the set of all surjective operators, in the local commutant. Similar results hold for the set of all complete wandering vectors and complete multi-Riesz vectors, when the surjective ...

Automatic Continuity of Higher Derivations on JB*-Algebras

Moment Sets and the Unitary Dual of a Nilpotent Lie Group

Let G be a connected and simply connected nilpotent Lie group with Lie algebra g and unitary dual Ĝ. The moment map for π ∈ Ĝ sends smooth vectors in the representation space of π to g∗. The closure of the image of the moment map for π is called its moment set. N. Wildberger has proved that the moment set for π coincides with the closure of the convex hull of the corresponding coadjoint orbit. ...