Reverse Harnack conjecture for non-null-homotopic harmonic mappings

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Let Ω⊂C\Omega\subset\mathbb C be a doubly connected domain, and let C∘=C∖{0}\mathbb C_\circ=\mathbb C\setminus\{0\}. Suppose h ⁣:Ω→C∘h\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

sup⁡Ω∣h∣inf⁡Ω∣h∣⩾cosh⁡(12Mod⁡Ω).\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.

References

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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