On arithmetical and dynamical properties of Lorentz maps of the torus
  We proved that any Lorentz transformation of 2-torus is Anosov automorphism. One completely describes admissible parameters of Lorentz transformations and their arithmetical properties. One proved that an admissible speed light parameter has a countable spectra accumulating to this parameter. 
S.Aranson, E.Zhuzhoma