Parallel Transport & Covariant Derivative: Overview

In summary, the conversation discusses the concept of a covariant derivative, which is a derivative operator that is not dependent on the chosen coordinate system. This allows for the removal of any artifacts arising from a particular coordinate system, ensuring that the rate of change of a tensor field along a manifold is itself a tensor field. It is also mentioned that a vector is said to be parallely transported along a curve if it remains constant as it moves along the curve, which can be translated into the mathematical statement that its directional derivative along the curve vanishes.
  • #1
"Don't panic!"
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I have been reading section 3.1 of Wald's GR book in which he introduces the notion of a covariant derivative. As I understand, this is introduced as the (partial) derivative operators [itex]\partial_{a}[/itex] are dependent on the coordinate system one chooses and thus not naturally associated with the structure of the manifold, therefore we introduce a new derivative operator [itex]\nabla_{a}[/itex] which fulfils this criteria. Intuitively, the covariant derivative is constructed in such a way as to remove any artefacts arising from any particular coordinate system, such that the rate of change of a tensor field in a direction along the manifold is itself a tensor field. Is this correct?

He then goes on to say that a vector [itex]\mathbf{v}^{a}[/itex] given at each point along a curve [itex]C[/itex] (with tangent vector [itex]\mathbf{t}^{a}[/itex]) is said to be parallely transported as one moves along the curve if the equation $$\mathbf{t}^{a}\nabla_{a}\mathbf{v}^{b}=0$$ is satisfied along the curve.
Intuitively, is this a statement that a vector [itex]\mathbf{v}^{a}[/itex] is parallely transported along the curve if it remains constant as it moves along the curve, this can be translated into the mathematical statement that its directional derivative along the curve vanishes, i.e. [itex]\mathbf{t}^{a}\nabla_{a}\mathbf{v}^{b}=0[/itex]. Is this correct?
 
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  • #2
Both of these seem like reasonable verbalizations to me.
 

Related to Parallel Transport & Covariant Derivative: Overview

What is parallel transport?

Parallel transport refers to the process of moving a vector or tensor along a path on a curved manifold while keeping it parallel to itself. This is necessary because vectors and tensors may change direction as they are transported over a curved surface, and parallel transport ensures that they maintain their original direction.

What is a covariant derivative?

A covariant derivative is a mathematical operation that takes into account the curvature of a manifold when differentiating a vector or tensor field. It measures the rate of change of a quantity along a given direction, taking into consideration how the direction itself changes as it moves across the manifold.

What is the difference between parallel transport and covariant derivative?

The main difference between parallel transport and covariant derivative is that parallel transport deals with moving a vector or tensor along a path while keeping it parallel to itself, while the covariant derivative involves calculating the rate of change of a vector or tensor field along a given direction on a curved manifold.

What are some real-world applications of parallel transport and covariant derivative?

Parallel transport and covariant derivative have various applications in fields such as physics, engineering, and computer science. For example, they are used in general relativity to describe the motion of particles in curved spacetime, in computer graphics to model deformations of objects, and in robotics to plan movements of robotic arms on curved surfaces.

What is the relationship between parallel transport and geodesics?

Geodesics are the shortest paths between two points on a curved surface, and parallel transport is used to keep a vector or tensor parallel to itself as it is transported along a geodesic. In other words, parallel transport is the process of moving a vector or tensor along a geodesic without changing its direction.

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