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Landau-type theorems for certain planar harmonic mappings or biharmonic mappings. (English) Zbl 1291.30127
Summary: In this article, we first establish three new coefficient inequalities for planar bounded harmonic mappings in the unit disc $U$. Then we derive two versions of Landau-type theorems for bounded planar harmonic mappings or biharmonic mappings by applying these coefficient inequalities, which improve the related results of earlier authors. In particular, our results for certain bounded planar harmonic mappings such that $|f(z)|\leqslant M$ for $z\in U$ are sharp when $M=1$.
MSC:
30C62Quasiconformal mappings in the plane
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