Let ( M , g ) be a Riemannian manifold. Extend the metric tensor g to the set of tangents TM with the following specification: if a,b∈TvTM(v∈TpM), then g~v(a,b):=gp(α˙(0),β˙(0))+gp(DαX(0),DβY(0)) where α,β are curves in M such that α(0)=β(0)=p. X and Y are vector fields along α,β respectively, with the condition X˙(0)=a,Y˙(0)=b. Dα and Dβ are the operators of the covariant derivative along the corresponding curves according to the Levi-Civita connection. Is the eigenfunction from the Riemannian manifold (M,g) to the Riemannian manifold (TM,g~) harmonic? differential geometrytopology