On the Ricci symmetries of a K\"ahler manifold

Abstract

The main purpose of the present paper is to investigate the symmetry properties of a K\"ahler manifold involving the Ricci tensor. In this context, the most symmetric manifolds are K\"ahler-Einstein spaces, and their natural generalizations are Ricci-parallel K\"ahler manifolds, Ricci-semisymmetric K\"ahler manifolds and holomorphically Ricci-pseudosymmetric K\"ahler manifolds. Unlike their Riemannian counterparts, we prove that all these conditions also admit a characterization solely in terms of holomorphic planes, analogously to the symmetries related to the Riemannian curvature tensor in K\"ahler manifolds. A key finding is that the concept of holomorphic Ricci pseudosymmetry is distinct from the classical Ricci-pseudosymmetric condition introduced by Deszcz. By carefully analyzing the interplay between these definitions, we clarify the precise geometric role of the so-called Ricci curvature of Deszcz. Additionally, we also present a geometric interpretation of the complex Tachibana-Ricci tensor and we establish a new criterion for a K\"ahler manifold to be Einstein based on holomorphic planes.