Quantitative estimates for the Bakry-Ledoux isoperimetric inequality

TL;DR

This paper proves a quantitative isoperimetric inequality for weighted Riemannian manifolds with Ricci curvature at least 1, extending isoperimetric results beyond Euclidean and Gaussian spaces using needle decomposition techniques.

Contribution

It provides the first quantitative isoperimetric inequality on noncompact spaces, utilizing Klartag's needle decomposition and a reverse Poincaré inequality for the guiding function.

Findings

Bound on volume difference between sets and level sets in terms of isoperimetric deficit.

First quantitative isoperimetric inequality on noncompact spaces.

Development of a reverse Poincaré inequality for the guiding function.

Abstract

We establish a quantitative isoperimetric inequality for weighted Riemannian manifolds with $\mathrm{Ric}_{\infty} \ge 1$. Precisely, we give an upper bound of the volume of the symmetric difference between a Borel set and a sub-level (or super-level) set of the associated guiding function (arising from the needle decomposition), in terms of the deficit in Bakry-Ledoux's Gaussian isoperimetric inequality. This is the first quantitative isoperimetric inequality on noncompact spaces besides Euclidean and Gaussian spaces. Our argument makes use of Klartag's needle decomposition (also called localization), and is inspired by a recent work of Cavalletti, Maggi and Mondino on compact spaces. Besides the quantitative isoperimetry, a reverse Poincar\'e inequality for the guiding function that we have as a key step, as well as the way we use it, are of independent interest.