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Martina Pfeifer

Chieu Minh Tran (Notre Dame): The inverse Kemperman problem

Thursday, 18.11.2021 11:00 im Raum via Zoom

Mathematik und Informatik

Let $G$ be a locally compact group with a left Haar measure $\mu$, and let $A,B \subseteq G$ be nonempty and compact. In 1964, Kemperman showed that if $G$ is unimodular (i.e., $\mu$ is also the right Haar measure, e.g., when $G$ is $\mathbb{R}/\mathbb{Z}$, $\mathrm{SL}_2(\mathbb{R})$, or $\mathrm{SO}_3(\mathbb{R})$), then $$ \mu(AB) \geq \min \{\mu(A)+\mu(B), \mu(G)\} .$$ The inverse Kemperman problem (proposed by Griesmer, Kemperman, and Tao) asks when the equality happens or nearly happens. I will discuss the recent solution of this problem by Jinpeng An, Yifan Jing, Ruixiang Zhang, and myself highlighting some ideas from model-theoretic group theory.



Angelegt am Thursday, 11.11.2021 10:14 von Martina Pfeifer
Geändert am Thursday, 11.11.2021 10:40 von Martina Pfeifer
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