Conjectured moduli of the quarter-sphere quadrilateral and its conjugate

Let QQ be the quadrilateral on the sphere whose boundary points are

z1=(0,0,1),z2=(1,0,0),z3=(12,12,0),z4=(12,12,0).z_1=(0,0,1),\quad z_2=(1,0,0),\quad z_3=\Big(\frac{1}{\sqrt{2}},\frac{1}{\sqrt{2}},0\Big),\quad z_4=\Big(-\frac{1}{\sqrt{2}},\frac{1}{\sqrt{2}},0\Big).

Let Q~\widetilde{Q} denote its conjugate quadrilateral, and let MM denote the modulus of such a quadrilateral.

Conjectured modulus values.

M(Q)=2,M(Q~)=12.M(Q)=\sqrt{2},\qquad M(\widetilde{Q})=\frac{1}{\sqrt{2}}.

The exact moduli are not known, but the paper reports considerable computational evidence for these values in the quarter-sphere problem.

Sources & referencesView supporting material

Primary source

Harri Hakula and Antti Rasila, “Laplace–Beltrami Equations and Numerical Conformal Mappings on Surfaces”, arXiv:2404.12743 (2024).

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