Bounded remainder sets
For a given sequence a boundedly expressible set is introduced. Three criteria concerning the Hausdorff dimension of such sets are proved.
For every irrational rotation we construct a coboundary which is continuous except at a single point where it has a jump, is nondecreasing, and has zero derivative almost everywhere.
In recent years, starting with the paper [B-D-S], we have investigated the possibility of characterizing countable subgroups of the torus by subsets of . Here we consider new types of subgroups: let be a Kronecker set (a compact set on which every continuous function can be uniformly approximated by characters of ), and the group generated by . We prove (Theorem 1) that can be characterized by a subset of (instead of a subset of ). If is finite, Theorem 1 implies our earlier result...