Thermodynamic Formalism and Singular Invariant Measures for Critical Circle Maps

As is well known, the renormalization group transformation in the space of analytic circle homeomorphisms with one cubic critical point and rotation number equal to the “golden section” has a single fixed point $T_0$. We construct the thermodynamic formalism for the critical map $T_0$ and use it to calculate the Hцlder indices for the singular invariant measure of $T_0$.