Measurable tilings
"Let (X,μ) be a standard probability space and G↷(X,μ) be a measure-preserving action of a group G on X.
The general problem that we consider is to understand the structure of measurable tilings F⊙A=X of X by a measurable tile A⊆X shifted by a finite set F⊆G, thus the shifts f⋅A, f∈F partition X up to null sets.
The motivation comes from the theory of (paradoxical) equidecompositions and tilings in Rn.
After a summary of recent results that concern the spheres Sd−1, where the action is given by rotations, and tori Td, where the action is given by translations, I will focus on the intersection of these cases, that is, the case of the circle S1=T1.
Using the structure theorem of Greenfeld and Tao for tilings of Zd, we show that measurable tilings of the circle can be reduced to tilings of finite cyclic groups.
This is a joint work with Conley and Pikhurko, and Greenfeld, Rozho\v{n} and Tao."