Contraction conjecture for positively curved spheres

Let (Sn,g,volg)(S^n,g,\operatorname{vol}_g) satisfy Ricgρg\operatorname{Ric}_g\geq\rho g with ρ>0\rho>0, and let gcanρg^\rho_{\mathrm{can}} be the canonical metric on SnS^n rescaled so that Ricgcanρ=ρgcanρ\operatorname{Ric}_{g^\rho_{\mathrm{can}}}=\rho g^\rho_{\mathrm{can}}. A map pushes forward one volume measure onto the other up to a finite constant if its pushforward is proportional to the target measure, and it contracts the corresponding metrics when it is 11-Lipschitz. Contraction conjecture. There exists a map

T:(Sn,gcanρ,volgcanρ)(Sn,g,volg)T:(S^n,g^\rho_{\mathrm{can}},\operatorname{vol}_{g^\rho_{\mathrm{can}}})\longrightarrow(S^n,g,\operatorname{vol}_g)

pushing forward volgcanρ\operatorname{vol}_{g^\rho_{\mathrm{can}}} onto volg\operatorname{vol}_g up to a finite constant and contracting the corresponding metrics. Such a map would imply the spherical spectral comparison conjecture by the contraction principle. The source attributes this as a previously unpublished conjecture and gives no resolution.

Sources & referencesView supporting material

Primary source

Emanuel Milman, “Spectral Estimates, Contractions and Hypercontractivity”, arXiv:1508.00606 (2018).

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