Reverse Harnack conjecture for non-null-homotopic harmonic mappings

From papers

Let ΩC\Omega\subset\mathbb C be a doubly connected domain, and let C=C{0}\mathbb C_\circ=\mathbb C\setminus\{0\}. Suppose h ⁣:ΩCh\colon\Omega\to\mathbb C_\circ is harmonic and is not homotopic to a constant through continuous mappings from Ω\Omega to C\mathbb C_\circ. Reverse Harnack conjecture. Then

supΩhinfΩhcosh(12ModΩ).\frac{\sup_{\Omega}|h|}{\inf_{\Omega}|h|}\geqslant\cosh\left(\frac{1}{2}\operatorname{Mod}\Omega\right).

If hh is additionally injective, the factor 1/21/2 should be omitted. This would extend the preceding sharp reverse Harnack estimate by removing the assumption that a boundary component is mapped homeomorphically onto the unit circle; the given text does not report a resolution.

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Sources & referencesView supporting material

Primary source

Tadeusz Iwaniec, Leonid V. Kovalev and Jani Onninen, “Doubly connected minimal surfaces and extremal harmonic mappings”, arXiv:0912.3542 (2010).

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