Liu–Ponnusamy conjectures on Bohr radii for harmonic quasi-subordination

From papers

Let D\mathbb D be the unit disk. Suppose that

f(z)=h(z)+g(z)=n=0anzn+n=2bnznf(z)=h(z)+\overline{g(z)}=\sum_{n=0}^{\infty}a_nz^n+\overline{\sum_{n=2}^{\infty}b_nz^n}

is a sense-preserving harmonic mapping in D\mathbb D and hφh\prec\varphi.

Liu–Ponnusamy's conjectures. (a) If φ\varphi is univalent and convex in D\mathbb D, then

n=1anrn+n=2bnrndist(φ(0),φ(D))\sum_{n=1}^{\infty}|a_n|r^n+\sum_{n=2}^{\infty}|b_n|r^n\leq \operatorname{dist}(\varphi(0),\partial\varphi(\mathbb D))

for z=rρc=0.299823|z|=r\leq\rho_c=0.299823\cdots, where ρc\rho_c is the positive root of

4r1r+2ln(1r)=1.\frac{4r}{1-r}+2\ln(1-r)=1.

(b) If φ\varphi is univalent in D\mathbb D, then the inequality in (a) holds for z=rρs=0.161353|z|=r\leq\rho_s=0.161353\cdots, where ρs\rho_s is the positive real root of

2r2(1r)2ln(1r)=14.\frac{2r^2}{(1-r)^2}-\ln(1-r)=\frac14.

These conjectures concern sharp Bohr-type radii for sense-preserving harmonic mappings, extending the corresponding finite-distortion results to the limiting case KK\to\infty; their resolution is not established in the supplied text.

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Sources & referencesView supporting material

Primary source

Ming-Sheng Liu, Saminathan Ponnusamy and Jun Wang, “Bohr's phenomenon for the classes of Quasi-subordination and K-quasiregular harmonic mappings”, arXiv:2004.08903 (2020).

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