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Maximal boundary rigidity for Alexandrov spaces

Maximal boundary rigidity for Alexandrov spaces

Start: 
Monday, November 25, 2024 12:00 pm
End: 
Monday, November 25, 2024 12:50 pm
Location: 
111 STAG
Qin Deng
MIT

Given an Alexandrov space with curvature bounded below by $K$, dimension $m$ and radius $r$, one may ask how large the boundary of X can be. In the case where $K=1$ and $r = \pi/2$, this is known as Lytchak’s problem and was answered by Petrunin, who showed the sharp upper bound $\mathcal{H}^{m-1}(\partial X) \leq \mathcal{H}^{m-1}(\mathbb{S}^{m-1})$. Rigidity was later analyzed by Grove-Petersen, who showed that in the case of equality $X$ must be a hemisphere or the intersection of two hemispheres. In this talk, I will address both the bound and rigidity for arbitrary $K$ and $r$

Contact: 
Chad Giusti