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Real zeros of positive semidefinite forms. I
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Product numerical range in a space with tensor product structure
We study operators acting on a tensor product Hilbert space and investigate their product numerical range, product numerical radius and separable numerical range. Concrete bounds for the productExpand
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Corners of normal matrices
We study various conditions on matricesB andC under which they can be the off-diagonal blocks of a partitioned normal matrix.
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Lecture Notes on Normal Dilations
Products of two normal operators
We obtain some necessary or sufficient conditions for an operator on a complex separable Hilbert space to be expressible as a product of two normal operators. For example, it is shown that if T isExpand
Numerical ranges and dilations
Denote by W(A) the numerical range of a bounded linear operator A. For two operators A and B (which may act on different Hilbert spaces), we study the relation between the inclusion relationExpand
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Sums of orthogonal projections
Abstract In this paper, we consider the problem of characterizing Hilbert space operators which are expressible as a sum of (finitely many) orthogonal projections. We obtain a special operator matrixExpand
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