1. On the ${\Ext}^2$-problem for Hilbert spaces
- Author
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Sánchez, Félix Cabello, Castillo, Jesús M. F., Corrêa, Willian H. G., Ferenczi, Valentin, and García, Ricardo
- Subjects
Mathematics - Functional Analysis ,46B25, 46M18 ,Mathematics::Functional Analysis ,FOS: Mathematics ,Functional Analysis (math.FA) - Abstract
We show that $\Ext^2(\ell_2, \ell_2)\neq 0$ in the category of Banach spaces. This solves a sharpened version of Palamodov's problem and provides a solution to the second order version of Palais problem. We also show that $\Ext^2(\ell_1, \K)\neq 0$ in the category of quasi Banach spaces which solves the four-space problem for local convexity.
- Published
- 2019
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