Remark on the rational functions having the same Julia set

Abstract

Let f and g two rational functions having the same Julia set J_f. Lets suppose that f has a rational indifferent periodic point and that the critical set of f is disjoint of J_f. Then or J_f has to be equal to P^1, a circle, an arc of a circle for some cordinate or f and g has to verify an equation of the type: $$f^{m_1}\circ g\circ f^{m_2}\circ\cdotc\circ f^{m_n}\circ g=f^m.$$