This is an announcement for the paper "Sharp isoperimetric inequalities and model spaces for curvature-dimension-diameter condition" by Emanuel Milman.

Abstract: We obtain new sharp isoperimetric inequalities on a Riemannian manifold equipped with a probability measure, whose generalized Ricci curvature is bounded from below (possibly negatively), and generalized dimension and diameter of the convex support are bounded from above (possibly infinitely). Our inequalities are \emph{sharp} for sets of any given measure and with respect to all parameters (curvature, dimension and diameter). Moreover, for each choice of parameters, we identify the \emph{model spaces} which are extremal for the isoperimetric problem. In particular, we recover the Gromov--L'evy and Bakry--Ledoux isoperimetric inequalities, which state that whenever the curvature is strictly \emph{positively} bounded from below, these model spaces are the $n$-sphere and Gauss space, corresponding to generalized dimension being $n$ and $\infty$, respectively. In all other cases, which seem new even for the classical Riemannian-volume measure, it turns out that there is no \emph{single} model space to compare to, and that a simultaneous comparison to a natural \emph{one parameter family} of model spaces is required, nevertheless yielding a sharp result.

Archive classification: math.DG math.FA math.MG

Mathematics Subject Classification: 32F32, 53C21, 53C20

Remarks: 36 pages

Submitted from: emanuel.milman@gmail.com

The paper may be downloaded from the archive by web browser from URL

http://front.math.ucdavis.edu/mod/304481

or

http://arXiv.org/abs/mod/304481