Upper and lower Fredholm spectra. I

Buoni, John J.; Harte, Robin; Wickstead, Tony

doi:10.1090/S0002-9939-1977-0454676-0

Upper and lower Fredholm spectra. I
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by John J. Buoni, Robin Harte and Tony Wickstead

Proc. Amer. Math. Soc. 66 (1977), 309-314

DOI: https://doi.org/10.1090/S0002-9939-1977-0454676-0

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Abstract:

Joint upper and lower Fredholm spectra are defined for n-tuples of bounded linear operators, and the upper Fredholm spectrum is represented both as the simultaneous eigenvalues and as the simultaneous approximate eigenvalues of an n-tuple of operators obtained by a Berberian-Quigley construction.

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