# Einstein tensor

This article defines a tensor (viz a section on a tensor bundle over the manifold) of type (0,2)

## Definition

### Given data

A manifold $M$ with a connection $\nabla$ on it. BY default, we may take a Riemannian manifold and consider the Levi-Civita connection on it.

### Definition part

The Einstein tensor is a $(0,2)$-tensor that takes as input two vector fields and outputs a scalar function, as follows.

$(X,Y) \mapsto Ric(X,Y) - (1/2)Rg(X,Y)$

where $Ric(X,Y)$ denotes the Ricci curvature tensor and $R$ denotes the scalar curvature function.