5 papers
The No-Core Principle for Stationary Actions and Ends of Stationary Random Subgroups
Yair Hartman, Nadav Kalma
We prove a No-Core Principle for stationary actions of countable groups. Namely, if a Borel set intersects almost every orbit in finitely many points and has positive measure, then…
Stabilizer Subgroups and the Simplicity of Reduced Crossed Products
Yair Hartman, Mehrdad Kalantar
Given a minimal action of a countable group on a compact space , we prove that if the reduced crossed product is simple, then there ex…
On the inclusion of bounded harmonic functions of random walks
Yair Hartman, Aranka Hrušková, Omer Segev
We investigate the conditions under which the space of bounded harmonic functions of a probability measure on a group is contained in that of another measure . We esta…
Retraction Theorems for Group Compactifications
Yair Hartman, Aranka Hrušková, Mehrdad Kalantar +1
We characterize group compactifications of discrete groups for which there exists an equivariant retraction onto the boundary. In particular, we prove an equivariant analogue of Br…
On the amenable subalgebras of group von Neumann algebras
Tattwamasi Amrutam, Yair Hartman, Hanna Oppelmayer
We approach the study of sub-von Neumann algebras of the group von Neumann algebra for countable groups from a dynamical perspective. It is shown that admits a m…