# Journal of Operator Theory

Volume 47, Issue 1, Winter 2002 pp. 79-95.

Tensor products and the semi-Browder joint spectra**Authors**: Enrico Boasso

**Author institution:**Departamento de Matematica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria Pab. I, (1428) Buenos Aires, Argentina

**Summary:**Given two complex Banach spaces $X_1$ and $X_2$, a tensor product of $X_1$ and $X_2$, $X_1\tilde{\otimes}X_2$, in the sense of J. Eschmeier ([5]), and two finite tuples of commuting operators, $S=(S_1,\ldots,S_n)$ and $T=(T_1,\ldots ,T_m)$, defined on $X_1$ and $X_2$ respectively, we consider the $(n+m)$-tuple of operators defined on $X_1\tilde{\otimes}X_2$, $(S\otimes I,I\otimes T)= (S_1\otimes I,\ldots ,S_n\otimes I,I\otimes T_1,\ldots ,I \otimes T_m)$, and we give a description of the semi-Browder joint spectra introduced by V. Kordula, V.Müller and V. Rakočević in [7] and of the split semi-Browder joint spectra (see Section 3) of the $(n+m)$-tuple $(S\otimes I ,I\otimes T)$, in terms of the corresponding joint spectra of $S$ and $T$. This result is in some sense a generalization of a formula obtained for other various Browder spectra in Hilbert spaces and for tensor products of operators and for tuples of the form $(S\otimes I ,I\otimes T)$. In addition, we also describe all the mentioned joint spectra for a tuple of left and right multiplications defined on an operator ideal between Banach spaces in the sense of [5].

**Keywords:**Semi-Fredholm, semi-Browder and split joint spectra

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