Divergence of Energy-momentum Tensor

In summary, the conversation discusses the method for proving that Maxwell's energy-momentum equation is divergence-free. There is uncertainty about whether Lagrangians or Einstein's tensor should be used, and there is also mention of a simpler way to expand the tensor. The proposed method involves writing out the equation and using the commutativity of the derivatives.
  • #1
ClaraOxford
6
0
How do you prove that Maxwell's energy-momentum equation is divergence-free?
I don't know whether or not I have to use Lagrangians or Eistein's tensor, or if there's a simlpler way of expanding out the tensor..

∂[itex]_{\mu}[/itex]T[itex]^{\mu\nu}[/itex]=0

T[itex]^{}\mu\nu[/itex]=F[itex]^{}\mu\alpha[/itex]F[itex]^{}\nu[/itex][itex]_{}\alpha[/itex]-1/4F[itex]^{}\alpha\beta[/itex]F[itex]_{}\alpha\beta[/itex][itex]\eta[/itex][itex]^{}\mu\nu[/itex]
 
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  • #2
I mean

∂[itex]_{\mu}[/itex]T[itex]^{\mu\nu}[/itex]=0

T[itex]^{\mu\nu}[/itex]=F[itex]^{\mu\alpha}[/itex]F[itex]^{\nu}[/itex][itex]_{\alpha}[/itex]-1/4F[itex]^{\alpha\beta}[/itex]F[itex]_{\alpha\beta}[/itex][itex]\eta[/itex][itex]^{\mu\nu}[/itex]
 
  • #3
Try writing [itex]F_{\mu\nu} = \partial_\mu A_\nu - \partial_\nu A_\mu[/itex] and using the commutativity of the derivatives.
 

FAQ: Divergence of Energy-momentum Tensor

What is the energy-momentum tensor?

The energy-momentum tensor is a mathematical object that describes the distribution of energy and momentum in a particular region of spacetime.

What is divergence of energy-momentum tensor?

The divergence of the energy-momentum tensor is a measure of how energy and momentum are changing over time and in different directions within a given region of spacetime.

What does the divergence of energy-momentum tensor tell us about a system?

The divergence of the energy-momentum tensor can tell us about the dynamics of a system, such as the flow of energy and momentum and how they are being exchanged between different parts of the system.

How is the divergence of energy-momentum tensor related to the laws of physics?

The divergence of the energy-momentum tensor is related to the laws of physics through the Einstein field equations, which describe the relationship between the curvature of spacetime and the distribution of matter and energy within it.

Why is the divergence of energy-momentum tensor important in cosmology?

The divergence of the energy-momentum tensor is important in cosmology because it helps us understand the evolution of the universe and the behavior of matter and energy on a large scale. It also plays a crucial role in the study of gravitational fields and their effects on the motion of celestial bodies.

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