Equidecomposability of Jordan domains under groups of isometries
Let denote the isometry group of . We prove that if G is a paradoxical subgroup of then there exist G-equidecomposable Jordan domains with piecewise smooth boundaries and having different volumes. On the other hand, we construct a system of Jordan domains with differentiable boundaries and of the same volume such that has the cardinality of the continuum, and for every amenable subgroup G of , the elements of are not G-equidecomposable; moreover, their interiors are not G-equidecomposable...