Contracted Christoffel Symbols

In summary, a discussion about solving the Einstein field equations led to the discovery of a contracted Christoffel symbol, represented by \Gamma\rho\mu\rho = ∂/∂x\mu of ln(\sqrt{g}). The sources mentioned also raised questions about whether this is an established property of Christoffel symbols and the meaning of g, which does not have indices. Further research on the topic is recommended, including exploring the possible connection to the determinant of the metric tensor.
  • #1
space-time
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I was looking up ways to solve the Einstein field equations when I came across a couple of sources.

http://www.thescienceforum.com/physics/30059-solving-einstein-field-equations.html

https://dl.dropboxusercontent.com/u/14461199/Light%20Deflection%20SM.pdf

If you look at these sources, you will notice that they both say that:

[itex]\Gamma[/itex][itex]\rho[/itex][itex]\mu[/itex][itex]\rho[/itex] = ∂/∂x[itex]\mu[/itex] of ln([itex]\sqrt{g}[/itex])

They call this a contracted Christoffel symbol.

Can anybody explain to me if this is actually an established property of Christoffel symbols or if this derivation of the contracted Christoffel symbol was just specific to the situation that the two sources were deriving?

If it is a property, then what is g? It has no indices, so it doesn't seem like a metric tensor.

Finally, how do you derive this property of Christoffel symbols if this is in fact a property?
 
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  • #2
Hi :smile:

I am still a beginner at GR. I can't answers your questions but I think that g is the determinant of the metric tensor.
 
  • #3
http://physics.stackexchange.com/questions/81453/general-relativity-christoffel-symbol-identity may be useful.
 

1. What are contracted Christoffel symbols?

Contracted Christoffel symbols are mathematical quantities used in differential geometry to represent the curvature of a space. They are derived from the Christoffel symbols, which are themselves derived from the metric tensor, and are used to calculate quantities such as the Riemann curvature tensor and the geodesic equation.

2. How are contracted Christoffel symbols used in physics?

Contracted Christoffel symbols are used in physics to describe the curvature of spacetime in general relativity. They are also used in other areas of physics, such as in the study of fluid dynamics and in the calculation of the equations of motion for particles in a curved space.

3. What do the indices in the contracted Christoffel symbols represent?

The indices in the contracted Christoffel symbols represent the different directions in a given space. For example, in a three-dimensional space, there are three indices representing the x, y, and z directions. The values of the contracted Christoffel symbols at a particular point represent the curvature of the space in those different directions.

4. How are contracted Christoffel symbols related to the metric tensor?

The contracted Christoffel symbols are derived from the metric tensor, which describes the distance between two points in a given space. The metric tensor is used to calculate the Christoffel symbols, and then the contracted Christoffel symbols are derived from the Christoffel symbols. This relationship allows for the calculation of the curvature of a space using the metric tensor.

5. Are contracted Christoffel symbols always non-zero?

No, contracted Christoffel symbols can be zero in certain cases. For example, in a flat space (such as a Euclidean space), all contracted Christoffel symbols will be zero. However, in curved spaces, the contracted Christoffel symbols will generally have non-zero values, indicating the presence of curvature.

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