A notion of the weighted $σ_k$-curvature for manifolds with density

Abstract

We propose a natural definition of the weighted $σ_k$-curvature for a manifold with density; i.e.\ a triple $(M^n,g,e^{-ϕ}\mathrm{dvol})$. This definition is intended to capture the key properties of the $σ_k$-curvatures in conformal geometry with the role of pointwise conformal changes of the metric replaced by pointwise changes of the measure. We justify our definition through three main results. First, we show that shrinking gradient Ricci solitons are local extrema of the total weighted $σ_k$-curvature functionals when the weighted $σ_k$-curvature is variational. Second, we characterize the shrinking Gaussians as measures on Euclidean space in terms of the total weighted $σ_k$-curvature functionals. Third, we characterize when the weighted $σ_k$-curvature is variational. These results are all analogues of their conformal counterparts, and in the case $k=1$ recover some of the well-known properties of Perelman's $\mathcal{W}$-functional.