How to Write T_{\mu v} for Energy-Momentum Tensor

In summary, the tensor $$T^{\mu v}$$ can be expressed as $$T^{\mu v}=\Pi^{\mu}\partial^v-g^{\mu v}\mathcal{L}$$ where $$g^{\mu v}$$ is the metric and $$\mathcal{L}$$ is the Lagrangian density. To write $$T_{\mu v}$$, one can use the relation $$T_{\mu v}=g_{\mu \rho}g_{v p}T^{\rho p}$$. However, simplifying this term, e.g. $$g_{\mu \rho}g_{v p}T^{\rho p}=g_{\mu \
  • #1
Diracobama2181
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What would be the energy-momentum tensor for lowered indices?
I know the tensor can be written as $$T^{\mu v}=\Pi^{\mu}\partial^v-g^{\mu v}\mathcal{L}$$ where $$g^{\mu v}$$ is the metric and $$\mathcal{L}$$ is the Lagrangian density, but how would I write $$T_{\mu v}$$? Would it simply be $$T_{\mu v}=g_{\mu \rho}g_{v p}T^{\rho p}$$? And if so, is there a way to simplify $$g_{\mu \rho}g_{v p}T^{\rho p}=g_{\mu \rho}g_{v p}(\Pi^{\rho}\partial^p-g^{\rho p}\mathcal{L})$$?
 
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Due to my poor study symmetry of the first term, e.g.
[tex]\Pi^\mu \partial^\nu = \Pi^\nu \partial^\mu[/tex]
was not clear to me. What are ##\Pi,\partial## ?
 
  • #3
anuttarasammyak said:
Due to my poor study symmetry of the first term, e.g.
[tex]\Pi^\mu \partial^\nu = \Pi^\nu \partial^\mu[/tex]
was not clear to me. What are ##\Pi,\partial## ?
Apologies, that should be $$\Pi^{\mu}\partial^{v}\phi$$ where $$\phi$$ is a field and $$\Pi^{\mu}=\frac{\partial \mathcal{L}}{\partial(\partial_{\mu}\phi)}$$. Originally had this posted to the High Energy subforum since this was originally a quantum field theory question, but someone moved it here.
 
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1. What is the Energy-Momentum Tensor?

The Energy-Momentum Tensor is a mathematical construct used in physics to describe the distribution of energy and momentum in a system. It is a symmetric tensor of rank 2, with 4 components representing energy density, energy flux, momentum density, and momentum flux.

2. How do I write Tμν for Energy-Momentum Tensor?

To write Tμν for Energy-Momentum Tensor, you need to use the Einstein field equations, which relate the curvature of spacetime to the energy and momentum within it. This equation can be written as Tμν = (c4/8πG)Gμν, where c is the speed of light and G is the gravitational constant.

3. What is the significance of Tμν in physics?

Tμν is significant in physics because it is a fundamental quantity used in Einstein's theory of general relativity. It describes the relationship between the curvature of spacetime and the distribution of energy and momentum, allowing us to understand the behavior of massive objects in the universe.

4. How is Tμν calculated for a specific system?

Tμν can be calculated for a specific system by using the energy and momentum density of the system, as well as the velocity and stress of the particles within it. These values can be plugged into the Einstein field equations to determine the components of Tμν.

5. Are there any alternative formulations for Tμν?

Yes, there are alternative formulations for Tμν in different theories of gravity, such as the teleparallel equivalent of general relativity. However, the Einstein field equations and the resulting Tμν are currently the most widely accepted and used in modern physics.

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