The partial Ricci flow on one-dimensional foliations
arXiv:1308.0985
Abstract
A flow of metrics, , on a manifold is a solution of a differential equation $\dt g = S(g)$, where a geometric functional is a symmetric -tensor usually related to some kind of curvature. The mixed sectional curvature of a foliated manifold regulates the deviation of leaves along the leaf geodesics. We introduce and study the flow of metrics on a foliation (called the 'Partial Ricci Flow'), where and is the partial Ricci curvature of the foliation; in other words, the velocity for a unit vector orthogonal to the leaf, , is the mean value of sectional curvatures over all mixed planes containing . The flow preserves totally geodesic foliations and is used to examine the question: Which foliations admit a metric with a given property of mixed sectional curvature (e.g., point-wise constant)? This is related to Toponogov question about dimension of totally geodesic foliations with positive mixed sectional curvature. We first consider a one-dimensional foliation, since this case is easier. We prove local existence/uniqueness theorem, deduce the government equations for the curvature and conullity tensors (which are parabolic along the leaves), and show convergence of solution metrics for some classes of almost-product structures. For the warped product initial metric the global solution metrics converge to one with constant mixed sectional curvature.
18 pages