nLab
stress-energy tensor

Context

Physics

physics, mathematical physics, philosophy of physics

Surveys, textbooks and lecture notes


theory (physics), model (physics)

experiment, measurement, computable physics

Contents

Idea

In a model (in theoretical physics) of gravity coupled to other fields, the energy momentum tensor or stress energy tensor T is the variation of the matter part S fieldsS_{fields} in the Einstein-Hilbert action with respect to the metric, δS fields=Tδg\delta S_{fields} = T \delta g.

It is a measure for the energy and momentum density of the matter contribution to the theory.

Since the variation of the Einstein-Hilbert action S EHS_{EH} is the Einstein tensor GG, the equations of motion of gravity, hence Einstein's equations assert that (up to constant prefactors)

G=T. G = T \,.

Properties

Renormalization and Vacuum energy

The renormalization freedom in perturbative quantization of gravity (perturbative quantum gravity) induces freedom in the choice of vacuum expectation value of the stress-energy tensor and hence in the cosmological constant.

For details see there.

Details

Last revised on February 9, 2018 at 07:02:24. See the history of this page for a list of all contributions to it.