Problems / geometry-topology
geometry-topology / Riemannian geometry; harmonic functions of polynomial growth
Yau's dimension comparison for harmonic functions of integer polynomial growth under nonnegative Ricci curvature
Theorem 1.1: there are an even n≥8 (the paper allows n=16), an integer k≥2 (k=50000) and a complete smooth metric on Rn with Ric≥0, Euclidean near the origin, asymptotic volume ratio strictly between 0 and 1, and hk>hk(Rn); the metric has nonunique tangent cones at infinity. Companion: in dimension three, for 4/9<v<1, 1<c<9v/4 and all large k, metrics with Ric≥0, AVR v and hk≥c(k+1)2, which can be made (1+ϵ)-bi-Lipschitz to Euclidean. The metric depends on k. Not shown: a single metric violating the bound for all large k, or anything about the finite-dimensionality results, which stand.