Abstract
Given Banach space operators A ∈ B(
) and B ∈ B(
), let A⊗B ∈ B(
⊗
) denote the tensor product of A and B. Let σ a , σ aw and σ ab denote the approximate point spectrum, the Weyl approximate point spectrum and the Browder approximate point spectrum, respectively. Then σ aw (A⊗B) ⊆ σ a (A)σ aw (B) ⊂ σ aw (A)σ a (B) ⊆ σ a (A)σ ab (B) ⊂ σ ab (A)σ a (B) = σ ab (A⊗B), and a sufficient condition for the (a-Weyl spectrum) identity σ aw (A⊗B) = σ a (A)σ aw (B) ⊂ σ aw (A)σ a (B) to hold is that σ aw (A⊗B) = σ ab (A⊗B). Equivalent conditions are proved in Theorem 1, and the problem of the transference of a-Weyl’s theorem for a-isoloid operators A and B to their tensor product A⊗B is considered in Theorem 2. Necessary and sufficient conditions for the (plain) Weyl spectrum identity are revisited in Theorem 3.
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Duggal, B.P., Djordjević, S.V. & Kubrusly, C.S. On the a-Browder and a-Weyl spectra of tensor products. Rend. Circ. Mat. Palermo 59, 473–481 (2010). https://doi.org/10.1007/s12215-010-0035-x
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DOI: https://doi.org/10.1007/s12215-010-0035-x