Conjecture on actions of circle homeomorphisms on spheres and discs

Let S1\mathbb{S}^{1} be the circle, S2\mathbb{S}^{2} the sphere, and D2\mathbb{D}^{2} the closed disc. Consider non-trivial actions of the group Homeo0(S1)\mathrm{Homeo}_{0}(\mathbb{S}^{1}) on these surfaces, and let φK,λS2\varphi_{K,\lambda}^{\mathbb{S}^{2}} and φK,λD2\varphi_{K,\lambda}^{\mathbb{D}^{2}} denote the families of actions referenced in the source. Sphere-and-disc action conjecture. Any non-trivial action of Homeo0(S1)\mathrm{Homeo}_{0}(\mathbb{S}^{1}) on the sphere is conjugate to one of the actions φK,λS2\varphi_{K,\lambda}^{\mathbb{S}^{2}}, and any non-trivial action on the closed disc is conjugate to one of the actions φK,λD2\varphi_{K,\lambda}^{\mathbb{D}^{2}}. The conjecture is motivated by the classification theorem for actions on the closed annulus and torus, but the source gives no resolution for the sphere or closed-disc cases.

Sources & referencesView supporting material

Primary source

Emmanuel Militon, “Actions of the group of homeomorphisms of the circle on surfaces”, arXiv:1211.0846 (2014).

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