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Given two complex Banach spaces $X_1$ and $X_2$, a tensor product $X_1\tilde{\otimes} X_2$ of $X_1$ and $X_2$ in the sense of [14], two complex solvable finite dimensional Lie algebras $L_1$ and $L_2$, and two representations $\rho_i\colon L_i\to {\rm L}(X_i)$ of the algebras, $i=1$, $2$, we consider the Lie algebra $L=L_1\times L_2$, and the tensor product representation of $L$, $\rho\colon L\to {\rm L}(X_1\tilde{\otimes}X_2)$, $\rho=\rho_1\otimes I +I\otimes \rho_2$. In this work we study the S{\l}odkowski and the split joint spectra of the representation $\rho$, and we describe them in terms of the corresponding joint spectra of $\rho_1$ and $\rho_2$. Moreover, we study the essential S{\l}odkowski and the essential split joint spectra of the representation $\rho$, and we describe them by means of the corresponding joint spectra and the corresponding essential joint spectra of $\rho_1$ and $\rho_2$. In addition, with similar arguments we describe all the above-mentioned joint spectra for the multiplication representation in an operator ideal between Banach spaces in the sense of [14]. Finally, we consider nilpotent systems of operators, in particular commutative, and we apply our descriptions to them.

Joint spectra of the tensor product representation of the direct sum of two solvable Lie algebras