Antisymmetric connection (Torsion Tensor)

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Discussion Overview

The discussion revolves around demonstrating that the expression Tabc = Γabc - Γacb represents a tensor of rank (1,2), specifically in the context of antisymmetric connections and the torsion tensor. The scope includes mathematical reasoning and technical explanations related to tensor calculus.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant proposes using the definition of the covariant derivative to show the tensor property but expresses difficulty in managing the resulting expressions.
  • Another participant questions the necessity of using covariant derivatives and suggests there are multiple methods to demonstrate the property.
  • A different participant suggests that raising indices to make tensors contravariant might be a viable approach, although they express uncertainty.
  • One participant emphasizes that the exercise aims to illustrate how the difference between two Christoffel symbols leads to the torsion tensor.
  • Another participant recommends examining the transformation equations for connection coefficients to understand how torsion transforms, referencing a specific equation from a resource.
  • A later post indicates that the original poster has resolved their issue, but details of the resolution are not provided.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method to demonstrate the tensor property, indicating multiple competing views and approaches remain in the discussion.

Contextual Notes

Participants express varying levels of familiarity with tensor calculus, and the discussion includes references to different textbooks and resources, suggesting a diversity of approaches and potential limitations in understanding.

psimeson
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How to show:

Tabc = \Gammaabc - \Gammaacb

is a Tensor of rank (1,2)

Attempted solution:
1. Using definition of Covariant Derivative:
DbTa= ∂aTa+\GammaabcTc (1)

DcTa= ∂cTa+\GammaacbTb (2)

I subtracted (2) from (1) but I couldn't really get a Tensor out of it. I just got lost in the mess.

Is this is the right way to start it?
 
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Do you have to use covariant derivatives in your problem? Is it a hint in your problem? There are several ways to show your property.

And why do you say "antisymmetric connection?"
 
I am also in the process of learning tensor calculus, so I may not be right, but wouldn't it work if you raised the indices and made every tensor ab-contravariant?
 
Which text are you using? There are different ways of showing your property, but the method should be adapted to what you already know.
 
@arkajad: Covariant derivative is not a hint in the problem. I am just trying to solve that way. I am following various kind of textbooks. So, any way would work for me.

@meldraft: I am sure if that will work. Since the purpose of this exercise is to show how the difference between two Christoffel symbols that are asymmetric gives rise to torsion tensor.
 
psimeson said:
@arkajad: Covariant derivative is not a hint in the problem. I am just trying to solve that way. I am following various kind of textbooks. So, any way would work for me.

Probably the simples way, for you, is to look at the transformation equations for the connection coefficients, and from that find out how the torsion will transform.

Check Eq. (3.6) in

http://preposterousuniverse.com/grnotes/grnotes-three.pdf

But do not read further than that!
 
Last edited by a moderator:
Solved.
 

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