August 2021 - Banach - mathdept.okstate.edu

Banach spaces webinar (with the zoom link)
by Sari, Bunyamin 25 Aug '21

25 Aug '21

zoom link for the webinar which was missing in the first email: https://unt.zoom.us/j/83807914306 Hello all, We are starting Banach spaces webinars for this academic year on Friday (8/27) with the following talk. Looking forward to seeing you all back. Best regards, Bunyamin For past talks and videos please see the webinar website: http://www.math.unt.edu/~bunyamin/banach ******** Speaker: Willian Corrêa (Universidade de São Paulo) Title: Two steps into the homology of $\ell_2$ Abstract. Enflo, Lindenstrauss and Pisier showed in 1975 the existence of a short exact sequence $0 \rightarrow \ell_2 \rightarrow X \rightarrow \ell_2 \rightarrow 0$ of Banach spaces and bounded linear operators in which $\ell_2$ is not complemented in $X$, i.e., $X \neq \ell_2$. This means that there is a non-Hilbertian Banach space with an isomorphic copy of $\ell_2$ such that the respective quotient is isomorphic to $\ell_2$ as well. In homological language, they showed that $Ext(\ell_2, \ell_2) \neq 0$. In this talk we discuss the next level of homology, i.e., we study exact sequences $0 \rightarrow \ell_2 \rightarrow X_1 \rightarrow X_2 \rightarrow \ell_2 \rightarrow 0$ and present the recent result that $Ext^2(\ell_2, \ell_2) \neq 0$. Joint work with Félix Cabello Sánchez, Jesús M. F. Castillo, Valentin Ferenczi and Ricardo García. The author was supported by FAPESP, processes 2016/25574-8 and 2018/03765-1.

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Annoucement
by Bentuo Zheng (bzheng) 25 Aug '21

25 Aug '21

Hi all, This is an open call for speakers for the webinar. If you wish to speak sometime in this academic year (September to May) please let me know so we can schedule it. Moreover, feel free to nominate speakers (e.g., grad students) who may not be on the email list. We had a very interesting two years of webinars with very impressive list of speakers and participants, and we wish to continue the tradition. Thank you all for your support. Best regards, Bunyamin

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Banach spaces webinar on Friday 8/27 by Willian Corrêa, Universidade de São Paulo
by Sari, Bunyamin 25 Aug '21

25 Aug '21

Hello all, We are starting Banach spaces webinars for this academic year on Friday (8/27) with the following talk. Looking forward to seeing you all back. Best regards, Bunyamin For past talks and videos please see the webinar website: http://www.math.unt.edu/~bunyamin/banach ******** Speaker: Willian Corrêa (Universidade de São Paulo) Title: Two steps into the homology of $\ell_2$ Abstract. Enflo, Lindenstrauss and Pisier showed in 1975 the existence of a short exact sequence $0 \rightarrow \ell_2 \rightarrow X \rightarrow \ell_2 \rightarrow 0$ of Banach spaces and bounded linear operators in which $\ell_2$ is not complemented in $X$, i.e., $X \neq \ell_2$. This means that there is a non-Hilbertian Banach space with an isomorphic copy of $\ell_2$ such that the respective quotient is isomorphic to $\ell_2$ as well. In homological language, they showed that $Ext(\ell_2, \ell_2) \neq 0$. In this talk we discuss the next level of homology, i.e., we study exact sequences $0 \rightarrow \ell_2 \rightarrow X_1 \rightarrow X_2 \rightarrow \ell_2 \rightarrow 0$ and present the recent result that $Ext^2(\ell_2, \ell_2) \neq 0$. Joint work with Félix Cabello Sánchez, Jesús M. F. Castillo, Valentin Ferenczi and Ricardo García. The author was supported by FAPESP, processes 2016/25574-8 and 2018/03765-1.

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