Debashish Goswami
Articles written in Proceedings – Mathematical Sciences
Volume 116 Issue 4 November 2006 pp 411-422 Operator Theory/Operator Algebras/Quantum Invariants
Invariants for normal completely positive maps on the hyperfinite II_{1} factor
Debashish Goswami Lingaraj Sahu
We investigate certain classes of normal completely positive (CP) maps on the hyperfinite II_{1} factor
Volume 119 Issue 1 February 2009 pp 63-70
On Equivariant Embedding of Hilbert $C^\ast$ Modules
We prove that an arbitrary (not necessarily countably generated) Hilbert $G-\mathcal{A}$ module on a $G-C^∗$ algebra $\mathcal{A}$ admits an equivariant embedding into a trivial $G-\mathcal{A}$ module, provided 𝐺 is a compact Lie group and its action on $\mathcal{A}$ is ergodic.
Volume 125 Issue 1 February 2015 pp 127-138
Let 𝐺 be one of the classical compact, simple, centre-less, connected Lie groups of rank 𝑛 with a maximal torus 𝑇, the Lie algebra $\mathcal{G}$ and let $\{E_{i},F_{i},H_{i},i=1,\ldots,n\}$ be tha standard set of generators corresponding to a basis of the root system. Consider the adjoint-orbit space $M=\{\text{Ad}_{g}(H_{1}), g\in G\}$, identified with the homogeneous space $G/L$ where $L=\{g\in G : \text{Ad}_{g}(H_{1})=H_{1}\}$. We prove that the coordinate functions $f_{i}(g):=\gamma_{i}(\text{Ad}_{g}(H_{1}))$, $i=1,\ldots,n$, where $\{\gamma_{1},\ldots,\gamma_{n}\}$ is basis of $\mathcal{G}'$ are `quadratically independent' in the sense that they do not satisfy any nontrivial homogeneous quadratic relations among them. Using this, it is proved that there is no genuine compact quantum group which can act faithfully on $C(M)$ such that the action leaves invariant the linear span of the above coordinate functions. As a corollary, it is also shown that any compact quantum group having a faithful action on the noncommutative manifold obtained by Rieffel deformation of 𝑀 satisfying a similar `linearity' condition must be a Rieffel-Wang type deformation of some compact group.
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