Parallel Transport Around Triangle on Sphere: Angles Excess 180°

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Discussion Overview

The discussion revolves around the concept of parallel transport of a vector around a triangle on a sphere, specifically addressing the relationship between the rotation of the vector and the excess of the sum of the triangle's angles over 180 degrees. The scope includes theoretical aspects of differential geometry.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant suggests using the Gauss-Bonnet theorem to relate the excess angle to the curvature of the sphere.
  • Another participant proposes starting with a coordinate system and writing down the metric for the 2D space to calculate the covariant derivative using the Christoffel connection.
  • A participant humorously implies that the original poster may be working on a specific assignment related to the topic.

Areas of Agreement / Disagreement

The discussion does not appear to reach a consensus, as participants offer different methods and approaches without agreeing on a single solution or perspective.

Contextual Notes

Participants mention the need to show the relationship between the excess angle and the covariant derivative, indicating potential dependencies on definitions and mathematical steps that remain unresolved.

Tzar
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Hey I got this problem. Any help wil be great.

Suppose you have a triangle on a sphere. Show that the amount by which a vector is rotated by a parallel transport around such a triangle equals the excess of the sum of the angles over 180 degrees.

Thanks!
 
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Anyone?? If you know some differential geometry, I am interested in your opinion!
 
Hey Tzar. What you need to use is the Gauss Bonet theorem. Once you've shown the excess angle is A/r^2 all you need to do is show that the covariant derivative is equal to this value.
 
Start off with a co-ordinate system. Write down the metric for your 2D space. Then calculate the covariant derivative (using the Christoffel connection), then stick it in the equation for parallel transports. Surely there's an easier way, but this method is most general.
 
doing the phys3550 assignment i take it :p
 

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