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Barycenters with a special weight function

Source: Miklós Schweitzer 2014, problem 9

December 23, 2014
functionintegrationadvanced fieldsadvanced fields unsolvedcollege contestsMiklos Schweitzerreal analysis

Problem Statement

Let ρ:RnR\rho:\mathbb{R}^n\to \mathbb{R}, ρ(x)=ex2\rho(\mathbf{x})=e^{-||\mathbf{x}||^2}, and let KRnK\subset \mathbb{R}^n be a convex body, i.e., a compact convex set with nonempty interior. Define the barycenter sK\mathbf{s}_K of the body KK with respect to the weight function ρ\rho by the usual formula sK=Kρ(x)xdxKρ(x)dx.\mathbf{s}_K=\frac{\int_K\rho(\mathbf{x})\mathbf{x}d\mathbf{x}}{\int_K\rho(\mathbf{x})d\mathbf{x}}. Prove that the translates of the body KK have pairwise distinct barycenters with respect to ρ\rho.