Some extremal algebras for hermitians
We study three extremal Banach algebras: (a) generated by two hermitian unitaries; (b) generated by an element of norm 1 all of whose odd positive powers are hermitian; (c) generated by an element of norm 1 all of whose even positive powers are hermitian. In all three cases the numerical range is found for various elements. The second algebra is shown to be isometrically isomorphic to a subalgebra of the first. The third algebra is identified with a space of functions.
1971 ◽
Vol 4
(2)
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pp. 193-200
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1986 ◽
Vol 28
(2)
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pp. 121-137
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1972 ◽
Vol 7
(2)
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pp. 307-308
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1989 ◽
Vol 12
(4)
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pp. 633-640
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1971 ◽
Vol 3
(1)
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pp. 27-33
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Keyword(s):
1985 ◽
Vol 28
(1)
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pp. 91-95
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Keyword(s):