tried to extend the classical theory of the dynamics associated
to the iteration of a rational function of a
complex variable to the more general setting of an arbitrary
semigroup of rational functions[1,2]. In this paper,
we will extend some results of the classical theory to
the semigroup of meromorphic functions.
1 Some Properties and Exceptional
Sets of a Semigroup Generated by a
Family of Meromorphic
Functions
Let G be a semigroup generated by a family of meromorphic
functions. For ˆ z C , we define the backward
orbit O í
(z) of z by
Oí
(z)={ there exists a gG such that g(w)=z} ˆ w C :
and the exceptional set of G is defined by
E(G)= { ˆ z C Oí
(z) is finite}.
Proposition 1 If z is not an element of E(G), then
O z( ) J(G).
Proof First of all, we prove ˆ gC O z ( ( ))
ˆCO z ( ) for any gG. For ˆ x CO z ( ), we need to
prove that ˆ g( ) ( ). x CO z Suppose that ( ) g x
ˆCO z ( )
f
, then there exists a sequence xnOí
(z) such
that and a sequence { ( )( ) g n x gx n o o n} in G