Grand uniqueness conjecture for the genus-zero and genus-one Canham problems

Let v0v_0 denote the reduced volume (isoperimetric ratio), with v0(0,1)v_0\in(0,1), and consider the Canham problem of minimizing the relevant Willmore-type energy among closed surfaces of genus gg subject to v=v0v=v_0, modulo homothety. The Clifford torus is

{[cosu,sinu,cosv,sinv]T2:u,v[0,2π]}S3,\left\{\frac{[\cos u,\sin u,\cos v,\sin v]^T}{\sqrt{2}}:u,v\in[0,2\pi]\right\}\subset\mathbb{S}^3,

and its surface of revolution representative in R3\mathbb{R}^3 is

T2={[(2+cosv)cosu,(2+cosv)sinu,sinv]:u,v[0,2π]}.T_{\sqrt{2}}=\left\{[(\sqrt{2}+\cos v)\cos u,(\sqrt{2}+\cos v)\sin u,\sin v]:u,v\in[0,2\pi]\right\}.

Grand uniqueness conjecture. The genus-g=0g=0 or 11 Canham problem with any isoperimetric ratio constraint v0(0,1)v_0\in(0,1) has a unique solution up to homothety. Moreover: (i) for g=0g=0 and each v0(0,1]v_0\in(0,1], the unique solution is a surface of revolution; (ii) for g=1g=1 and each v0(0,32(2π2)1/4]v_0\in\left(0,\frac{3}{2}(2\pi^2)^{-1/4}\right], the unique solution is a surface of revolution; and (iii) for g=1g=1 and each v0[32(2π2)1/4,1)v_0\in\left[\frac{3}{2}(2\pi^2)^{-1/4},1\right), the unique solution is a stereographic image in R3\mathbb{R}^3 of the Clifford torus in S3\mathbb{S}^3, equivalently a Möbius transformation of T2T_{\sqrt{2} }. At v0=1v_0=1 and g=0g=0, the solution is the round sphere; at v0=1v_0=1 and g1g\geqslant1, no solution exists by the isoperimetric inequality. Numerical and variational evidence supports uniqueness in the stated genus-zero and genus-one regimes, while a complete proof remains open.

Sources & referencesView supporting material

Primary source

Thomas Yu and Jingmin Chen, “On the Uniqueness of Clifford Torus with Prescribed Isoperimetric Ratio”, arXiv:2003.13116 (2020).

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