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A Geometric Characterization of Nonnegative Bands

Published online by Cambridge University Press:  20 November 2018

Alka Marwaha*
Affiliation:
Department of Mathematics Jesus and Mary College (University of Delhi) Chanakyapuri New Delhi - 110 021 India, email: [email protected]
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Abstract

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A band is a semigroup of idempotent operators. A nonnegative band $\mathcal{S}$ in $B({{L}^{2}}(X))$ having at least one element of finite rank and with rank $(S)\,>\,1$ for all $S$ in $\mathcal{S}$ is known to have a special kind of common invariant subspace which is termed a standard subspace (defined below).

Such bands are called decomposable. Decomposability has helped to understand the structure of nonnegative bands with constant finite rank. In this paper, a geometric characterization of maximal, rank-one, indecomposable nonnegative bands is obtained which facilitates the understanding of their geometric structure.

Keywords

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2004

References

[1] Choi, M. D., Nordgren, E. A., Radjavi, H., Rosenthal, P. and Zhong, Y., Triangularizing semigroups of quasinilpotent operators with nonnegative entries. Indiana Univ.Math. J. 42 (1993), 1525.Google Scholar
[2] Fillmore, P., MacDonald, G., Radjabalipour, M., and Radjavi, H., Towards a classification of maximal unicellular bands. Semigroup Forum 49 (1994), 195215.Google Scholar
[3] Fillmore, P., MacDonald, G., Radjabalipour, M., and Radjavi, H., On principal-ideal bands. Semigroup Forum, to appear.Google Scholar
[4] Marwaha, A., Decomposability and structure of nonnegative bands in infinite dimensions. J. Operator Theory 47 (2002), 3761.Google Scholar
[5] Radjavi, H., On reducibility of semigroups of compact operators. Indiana Univ.Math. J. 39 (1990), 499515.Google Scholar