Differentiability and weighted Laplacian formula on RCD spaces

Let (X,d,m)(X,\mathsf{d},\mathfrak{m}) be the RCD space under discussion, let k=dim(X,d,m)k=\dim(X,\mathsf{d},\mathfrak{m}), and let Rk\mathcal{R}_k^* be the full-measure regular set. Let ϕ\phi be the function defined by equation (9), and for fD(Δ)f\in D(\Delta) let Hessf\mathrm{Hess}_f be its Hessian. Differentiability and weighted Laplacian conjecture. The function ϕ\phi is differentiable for m\mathfrak{m}-almost every xRkx\in\mathcal{R}_k^*. Moreover, for every fD(Δ)f\in D(\Delta),

Δf(x)=tr(Hessf)(x)+logϕ,f(x)\Delta f(x)=\operatorname{tr}(\mathrm{Hess}_f)(x)+\langle\nabla\log\phi,\nabla f\rangle(x)

holds for m\mathfrak{m}-almost every xXx\in X. This is the paper's final conjecture, giving a pointwise weighted correction to the Laplacian–Hessian trace identity; the supplied context gives no resolution.

Sources & referencesView supporting material

Primary source

Shouhei Honda, “Collapsed Ricci limit spaces as non-collapsed RCD spaces”, arXiv:2002.08612 (2020).

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