On the boundaries of the Arnold tongues

If F is an increasing homeomorphism of the real line with the property that F(x+1)=F(x)+1 for any x, then F induces an orientation preserving circle homeomorphism f. The average amount by which each point on the real line is translated under the action of F is called the translation number of F, similarly the average angle by which every point on the circle is rotated by the action of f is called its rotation number. In this talk we study the parameter space of certain two parameter family of analytic circle diffeomorphism with the help of rotation numbers.