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Dynamics of meromorphic functions with direct or logarithmic singularities. (English) Zbl 1174.37011

Summary: Let \(f\) be a transcendental meromorphic function and denote by \(J(f)\) the Julia set and by \(I(f)\) the escaping set. We show that if \(f\) has a direct singularity over infinity, then \(I(f)\) has an unbounded component and \(I(f)\cap J(f)\) contains continua. Moreover, under this hypothesis \(I(f)\cap J(f)\) has an unbounded component if and only if \(f\) has no Baker wandering domain. If \(f\) has a logarithmic singularity over infinity, then the upper box dimension of \(I(f)\cap J(f)\) is 2 and the Hausdorff dimension of \(J(f)\) is strictly greater than 1. The above theorems are deduced from more general results concerning functions which have ’direct or logarithmic tracts’, but which need not be meromorphic in the plane. These results are obtained by using a generalization of the Wiman-Valiron theory. This method is also applied to complex differential equations.

MSC:

37F10 Dynamics of complex polynomials, rational maps, entire and meromorphic functions; Fatou and Julia sets
30D05 Functional equations in the complex plane, iteration and composition of analytic functions of one complex variable
30D20 Entire functions of one complex variable (general theory)
30D30 Meromorphic functions of one complex variable (general theory)
34M05 Entire and meromorphic solutions to ordinary differential equations in the complex domain
37F50 Small divisors, rotation domains and linearization in holomorphic dynamics