Milman's spectral conjecture for positively Ricci-curved spheres

From papers

Let dd be a positive integer, let (Sd,g)(\mathbb{S}^d,g) be a Riemannian sphere, and let volg\operatorname{vol}_g denote its volume measure. Suppose that

Ricgρg\operatorname{Ric}_g\geq \rho g

for some ρ>0\rho>0. Let gcanρg^\rho_{\mathrm{can}} be the canonical metric on Sd\mathbb{S}^d rescaled so that

Ricgcanρ=ρgcanρ.\operatorname{Ric}_{g^\rho_{\mathrm{can}}}=\rho g^\rho_{\mathrm{can}}.

Here λk(Sd,g,volg)\lambda_k(\mathbb{S}^d,g,\operatorname{vol}_g) denotes the kkth eigenvalue in the relevant weighted spectral problem. Milman's spectral conjecture. For every k1k\geq 1,

λk(Sd,g,volg)λk(Sd,gcanρ,volgcanρ).\lambda_k(\mathbb{S}^d,g,\operatorname{vol}_g)\geq\lambda_k(\mathbb{S}^d,g^\rho_{\mathrm{can}},\operatorname{vol}_{g^\rho_{\mathrm{can}}}).

This is one of Milman's proposed finite-dimensional extensions of the Gaussian contraction paradigm. The paper states that its corresponding conjecture is false in general, so this spectral claim is refuted.

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Sources & referencesView supporting material

Primary source

Shrey Aryan, “Spectral Obstructions to Contracting Transport Maps on Curved Spaces”, arXiv:2605.24705 (2026).

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