Abstract
Landau gave a lower estimate for the radius of a schlicht disk centered at the origin and contained in the image of the unit disk under a bounded holomorphic function f normalized by f(0) = f′(0) − 1 = 1. Chen, Gauthier, and Hengartner established analogous versions for bounded harmonic functions. We improve upon their estimates.
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Dorff, M., Nowak, M. Landau’s Theorem for Planar Harmonic Mappings. Comput. Methods Funct. Theory 4, 151–158 (2004). https://doi.org/10.1007/BF03321062
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DOI: https://doi.org/10.1007/BF03321062