7 research outputs found

    Rank properties of exposed positive maps

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    Let \cK and \cH be finite dimensional Hilbert spaces and let \fP denote the cone of all positive linear maps acting from \fB(\cK) into \fB(\cH). We show that each map of the form Ο•(X)=AXAβˆ—\phi(X)=AXA^* or Ο•(X)=AXTAβˆ—\phi(X)=AX^TA^* is an exposed point of \fP. We also show that if a map Ο•\phi is an exposed point of \fP then either Ο•\phi is rank 1 non-increasing or \rank\phi(P)>1 for any one-dimensional projection P\in\fB(\cK).Comment: 6 pages, last section removed - it will be a part of another pape
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