Computing a Solution of Feigenbaum's Functional Equation in Polynomial   Time
  Lanford has shown that Feigenbaum's functional equation has an analytic solution. We show that this solution is a polynomial time computable function. This implies in particular that the so-called first Feigenbaum constant is a polynomial time computable real number. 
Peter Hertling (Universitaet der Bundeswehr Muenchen), Christoph   Spandl (Universitaet der Bundeswehr Muenchen)
math.DS cs.CC cs.NA