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Abstract

Suppose that f1, ¼, fmf_1, \ldots , f_m satisfy functional equations of type¶¶ fi(zd) = Pi(z, fi(z))     or     fi(z) = Pi(z, fi(zd))f_i({z^d}) = P_i(z, f_i(z)) \quad {or} \quad f_i(z) = P_i(z, f_i({z^d})) ¶for i = 1, ¼, mi = 1, \ldots , m, an integer d > 1 and polynomials Pi Î \Bbb C (z)[ y]P_i \in \Bbb C (z)[ {y}] with pairwise distinct partial degrees degy( P1), ¼, degy( Pm)\deg _y( {P_1}), \ldots , \deg _y( {P_m}). Generalizing a result of Keiji Nishioka and using an idea of Kumiko Nishioka we show, that f1, ¼, fmf_1, \ldots , f_m can only be algebraically dependent over \Bbb C (z)\Bbb C (z), if there is an index k Î { 1, ¼, m}\kappa \in \{ {1, \ldots , m}\} such that fkf_{\kappa } is rational.

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