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arXiv · 2008.12322

Pairs of projections and commuting isometries

Sandipan De·Shankar. P·Jaydeb Sarkar·Sankar T. R
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Abstract

It is known that the non-zero part of compact defect operators of Berger-Coburn-Lebow pairs (BCL pairs in short) of isometries are diagonal operators of the form \[ \begin{bmatrix} I_1 & & & \\ & D & & \\ & & - I_2 & \\ & & & - D \\ \end{bmatrix}, \] where $I_1$ and $I_2$ are the identity operators and $D$ is a positive contractive diagonal operator. We discuss the question of constructing an irreducible BCL pair from a diagonal operator of the above type. The answer to this question is sometimes in the affirmative and sometimes in the negative. This also answers a part of the question raised by He, Qin, and Yang. Our explicit constructions of BCL pairs yield concrete examples of pairs of commuting isometries.

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Sandipan De, Shankar. P, Jaydeb Sarkar, Sankar T. R. 2020-08-27. Pairs of projections and commuting isometries. https://arxiv.org/abs/2008.12322

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