A new approach to gradient Ricci solitons and generalizations

Abstract

This short note concerns with two inequalities in the geometry of gradient Ricci solitons $(g,f,\lambda )$ on a smooth manifold $M$. These inequalities provide some relationships between the curvature of the Riemannian metric $g$ and the behavior of the scalar field $f$ through two second order equations satisfied by the scalar $\lambda$. We propose several generalizations of Ricci solitons to the setting of manifolds endowed with linear connections, not necessary of metric type.

revised and expanded version