5 problems

Let $X$ be a locally compact CAT(0) space with a geometric group action $\Gamma\curvearrowright X$. An $n$-flat is an isometrically embedded copy of Euclidean $n$-space, where…

Large-cohomogeneity diameter conjecture. For every $\epsilon>0$ and all sufficiently large $k$ with $n>k$,

Let $(M,\partial M)$ be an $n$-manifold with contractible components that admits a geometric group action, and let $L^2H_i(M)$ denote its $L^2$-homology. Manifold cocompact action…

For a discrete group $G$, let $L^2H_i(G)$ denote the $L^2$-homology of a contractible $G$-space, and let $\operatorname{cadim}(G)$ be the least dimension of a contractible $G$-mani…

For a discrete group $G$, let $L^2H_i(G)$ denote the $L^2$-homology of a contractible $G$-space, and let $\operatorname{actdim}(G)$ be the least dimension of a contractible manifol…