Šarkovského věta a diferenciální rovnice
Šarkovského věta a diferenciální rovnice. II
Smooth conjugacy classes of circle diffeomorphisms with irrational rotation number
We prove the C¹-density of every -conjugacy class in the closed subset of diffeomorphisms of the circle with a given irrational rotation number.
Substitutions on two letters, cutting segments and their projections
In this paper we study the structure of the projections of the finite cutting segments corresponding to unimodular substitutions over a two-letter alphabet. We show that such a projection is a block of letters if and only if the substitution is Sturmian. Applying the procedure of projecting the cutting segments corresponding to a Christoffel substitution twice results in the original substitution. This induces a duality on the set of Christoffel substitutions.