New Kronecker–Weyl type equidistribution results and Diophantine approximation

Abstract

An interesting result of Veech more than 50 years ago is a parity, or mod 2, version of the Kronecker–Weyl equidistribution theorem concerning the irrational rotation sequence {qalpha }, q=0,1,2,3,ldots If alpha is badly approximable and bin (0,1) satisfies bne {malpha } for any min {mathbb {Z}}, then the parity of cardinalities of the sets {1leqslant qleqslant N,{:},{qalpha }in [0,b)} as Nrightarrow infty is evenly distributed. We first answer a question of Veech and establish a stronger form of the mod n analog of his result. Furthermore, for irrational alpha and b={malpha } for some min {mathbb {N}}, we give a simple yet precise characterization of those cases that give rise to even distribution. We also obtain time-quantitative description of some very striking violations of uniformity—this part is particularly number theoretic in nature, and involves Ostrowski representations of positive integers and alpha -expansions of real numbers. The Veech discrete 2-circle problem can also be visualized as a problem that concerns 1-direction geodesic flow on a surface obtained by modifying the surface comprising two side-by-side squares by the inclusion of symmetric barriers and gates on the vertical edges, with appropriate modification of the vertical edge identifications. We establish a far-reaching generalization of this case to ones that concern 1-direction geodesic flow on surfaces obtained by modifying a finite square tiled translation surface in analogous but not necessarily symmetric ways.