Published online by Cambridge University Press: 22 January 2016
Consider a single-valued meromorphic function w = f(p) defined on an open Riemann surface R with an ideal boundary β. In [1], Collingwood and Cartwright introduced the global cluster set for a function meromorphic on the unit disk. Generalizing the definition of global cluster sets to our present setting, we define the global cluster set for w = f(p) as follows;
A value w in the extended complex plane is called a cluster value at β if there exists a sequence in R converging to β such that