On infinitesimal concircular transformations

In 1940 to 42, K. Yano [5] introduced the concept of concircular transformations of Riemannian manifolds and developed the theory of the concircular geometry. Recently, we have discussed concircular transformations in Riemannian manifolds, complete or compact [1]. We shall in the present paper introduce the notion of infinitesimal concircular transformations and study the properties of Riemannian monifolds, compact, complete or comformally complete, admitting an infinitesimal concircular transformotion.