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The spectral picture of (LA, RB)
Journal article   Open access   Peer reviewed

The spectral picture of (LA, RB)

Raúl E Curto and Lawrence A Fialkow
Journal of Functional Analysis, Vol.71(2), pp.371-392
1987
DOI: 10.1016/0022-1236(87)90010-3
url
https://doi.org/10.1016/0022-1236(87)90010-3View
Published (Version of record) Open Access

Abstract

Let A and B be commuting n -tuples of operators on a Hilbert space H , and let ( L A , R B ) be the (2 n )-tuple of left and right multiplications induced by A and B on L(H) . We show that σ T ((L A ,R B ), L(H)) = σ T (A,H) × σ T (B,H) , σ Te ((L A ,R B ), L(H)) = [σ Te (A,H) × σ T (B,H)]∪[σ T (A,H) × σ Te (B,H)] , and ind( L A , R B ) = (−1) n ind( A )ind( B ), whenever A and B are Fredholm. Similar results hold for the restrictions of ( L A , R B ) to norm ideals in L(H) , giving in particular the spectral picture of ( A ⊗ I , I ⊗ B ) on H ⊗ H . A. S. Fainstein, working independently, has announced versions of these results for Banach spaces.

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