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Gigli's characterization of Alexandrov curvature
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Gigli’s characterization of Alexandrov curvature. Proves Gigli's conjecture: in every integer dimension n ≥ 2, Alexandrov curvature at least κ is characterized by the full-support $\mathop{\mathrm{RCD}}\nolimits ((n-1)\kappa,n)$ condition with reference measure $\mathcal H^n$ and distributional sectional curvature at least κ in the original global test classes. The RCD condition is unreduced.

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released 2026-09-24  |  6 theorems · 29 lemmas · 39 proofs · 22,881 words  |  PLAY LEVEL 1 »  (pdf)
For every integer n ≥ 2 and κ ∈ ℝ, we prove that a complete separable metric space is an n-dimensional Alexandrov space of curvature at least κ if and only if, with reference measure $\mathcal H^n$, it is a full-support $\mathrm{RCD}((n-1)\kappa,n)$ space whose distributional sectional curvature is at least κ in Gigli's original global test classes. This resolves Gigli's characterization conjecture in dimensions at least two.
released 2026-09-24  |  1 theorem · 2 lemmas · 4 proofs · 4,356 words  |  PLAY LEVEL 2 »  (pdf)
On a full-support $\mathrm{RCD}(K,N)$ space with $1\lt N\lt \infty$, we prove that a bounded globally Lipschitz function whose distributional Hessian is bounded above by a bounded continuous function satisfies the corresponding second-derivative inequality along every minimizing geodesic.

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