Pullback of Vector Field in Relativity: Restrictions?

In summary, coordinate transformations in differential geometry must be one-to-one and invertible. This means that there is no restriction on pushforwarding or pullbacking any desired fields within the context of these transformations. However, it is important to note that pushforwards and pullbacks deal with maps between manifolds, not just coordinate transformations. In the case of a smooth map from a manifold onto itself, such as defined by the flow of a vector field, both pushforwards and pullbacks can be made in either direction based on the function or its inverse. This is necessary for calculations such as Lie derivatives of general tensors.
  • #1
Pencilvester
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TL;DR Summary
Shouldn’t the pullback of a vector (and pushforward of scalar and form, etc.) be easily definable for coordinate transformations?
Since coordinate transformations should be one-to-one and therefore invertible, wouldn’t there be no restriction on pushforwarding or pullbacking whatever fields we feel like (within the context of coordinate transformations)?
 
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  • #2
Pullbacks and pushforwards in differential geometry deal with maps between manifolds, not coordinate transformations.

That being said, if you have a smooth map from a manifold onto itself (such as defined by the flow of a vector field), then you can make pushforwards in either direction based on the function or its inverse. This is necessary for example for Lie derivatives of general tensors.
 
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  • #3
Just wanted to make sure, thanks!
 

1. What is the concept of pullback of vector field in relativity?

The pullback of a vector field in relativity is a mathematical operation that involves transforming a vector field from one coordinate system to another. It is used to study the behavior of vector fields in different reference frames, and it is an important tool in the theory of relativity.

2. What are the restrictions on the pullback of vector fields in relativity?

There are several restrictions on the pullback of vector fields in relativity. First, the coordinate transformation must be smooth and invertible. Additionally, the vector field must be well-defined and continuous in both coordinate systems. Finally, the pullback must preserve the metric structure of spacetime.

3. How does the pullback of vector fields relate to the principle of general covariance?

The principle of general covariance in relativity states that the laws of physics should be independent of the choice of reference frame. The pullback of vector fields is a mathematical tool that allows us to transform physical quantities, such as vector fields, between different reference frames while maintaining their physical properties. Therefore, the pullback is closely related to the principle of general covariance.

4. Can the pullback of vector fields be applied to all types of vector fields in relativity?

Yes, the pullback of vector fields can be applied to all types of vector fields in relativity, including timelike, spacelike, and null vector fields. As long as the vector field is well-defined and continuous in both coordinate systems, the pullback can be performed.

5. What are some practical applications of the pullback of vector fields in relativity?

The pullback of vector fields has many practical applications in relativity. It is used to study the behavior of physical quantities, such as energy and momentum, in different reference frames. It is also used in the calculation of gravitational fields and the analysis of spacetime curvature. Additionally, the pullback is essential in the formulation of the laws of physics in a covariant manner, as required by the principle of general covariance.

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