Extrinsic Geometry of a Riemannian Manifold and Ricci Solitons

The object of this paper is to find a vector field ξ and a constant λ on an n-dimensional compact Riemannian manifold Mn,g such that we obtain the Ricci soliton Mn,g,ξ,λ. In order to achieve this objective, we choose an isometric embedding provided in the work of Kuiper and Nash in the Euclidean space Rm,g¯ and choose ξ as the tangential component of a constant unit vector on Rm and call it a Kuiper–Nash vector. If τ is the scalar curvature of the compact Riemannian manifold Mn,g with a Kuiper–Nash vector ξ, we show that if the integral of the function ξτ has a suitable lower bound containing a constant λ, then Mn,g,ξ,λ is a Ricci soliton; we call this a Kuiper–Nash Ricci soliton. We find a necessary and sufficient condition involving the scalar curvature τ under which a compact Kuiper–Nash Ricci soliton Mn,g,ξ,λ is a trivial soliton. Finally, we find a characterization of an n-dimensional compact trivial Kuiper–Nash Ricci soliton Mn,g,ξ,λ using an upper bound on the integral of divξ2 containing the scalar curvature τ.