Introduction to the mathematics of general relativity: Difference between revisions

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[[File:StressEnergyTensor contravariant.svg|right|250px|thumb|Contravariant components of the stress–energy tensor.]]

The '''stress–energy tensor''' (sometimes '''stress–energy–momentum tensor''' or '''energy–momentum tensor''') is a [[tensor]] quantity in [[physics]] that describes the [[density]] and [[flux]] of [[energy]] and [[momentum]] in [[spacetime]], generalizing the [[stress (physics)|stress tensor]] of Newtonian physics. It is an attribute of [[matter]], [[radiation]], and non-gravitational [[force field (physics)|force fields]]. The stress–energy tensor is the source of the [[gravitational field]] in the [[Einstein field equations]] of [[general relativity]], just as mass density is the source of such a field in [[Newtonian gravity]]. Because this tensor has 2 indices (see next section) the Riemann curvature tensor has to be contracted into the Ricci tensor, also with 2 indices.

==Einstein equation==