Vector field and differential form confusion

  • #1
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Homework Statement
We have xy-plane, which is has a mapping (x,y). Another map is (u,v) and the transformation of coordinates are u=4x+3y and v=x+y.

1. Write vector field \frac{\partial}{\partial u} in the map (x,y)

2. Write the 1-form du in the map (x,y)
Relevant Equations
u=4x+3y and v=x+y.
Here is a picture of the solution I made :

1697563788231.png
So my question is: Are these right and how do they differ from each other?
 
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  • #2
In a formal Mathematical sense, they're duals to each other. Differential forms are evaluated at Vector Fields to produce numbers.
 
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  • #3
## \text { The first thing: } ##
## \frac { \partial } { \partial u } \text { is not a vector field. } ##

## \text { The second thing: } ##
## \text { The expression } \frac { \partial } { \partial u } = \frac { \partial u } { \partial x } \frac { \partial } { \partial x } + \frac { \partial u } { \partial y } \frac { \partial } { \partial y } \text { is not a correct expression. } ##
## \text { It should be } \frac { \partial } { \partial u } = \frac { \partial x } { \partial u } \frac { \partial } { \partial x } + \frac { \partial y } { \partial u } \frac { \partial } { \partial y } \text { where } x \text { and } y \text { are functions of } u \text { and } v \text { . } ##
 
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Related to Vector field and differential form confusion

What is the difference between a vector field and a differential form?

A vector field assigns a vector to every point in a space, representing, for example, the velocity of a fluid at each point. A differential form, on the other hand, is a mathematical object that can be integrated over a manifold and is used to generalize the concepts of functions and vector fields. Differential forms are often used in the context of integration and Stokes' theorem.

How do you convert a vector field to a differential form?

To convert a vector field to a differential form, you use the musical isomorphisms (often denoted by ♭ and ♯). For a vector field \( \mathbf{v} \), the corresponding 1-form \( \mathbf{v}^\flat \) is obtained by applying the metric tensor to \( \mathbf{v} \). In coordinates, if \( \mathbf{v} = v^i \partial_i \), then \( \mathbf{v}^\flat = v_i \, dx^i \) where \( v_i = g_{ij} v^j \) and \( g_{ij} \) is the metric tensor.

Why are differential forms important in physics?

Differential forms are crucial in physics because they provide a natural and coordinate-free way to describe physical laws. They are especially important in the formulation of electromagnetism, fluid dynamics, and general relativity. Differential forms facilitate the use of Stokes' theorem, which generalizes the fundamental theorem of calculus to higher dimensions and is essential in deriving many physical laws.

What is the exterior derivative and how does it relate to vector fields and differential forms?

The exterior derivative is an operation on differential forms that generalizes the concept of taking the gradient, curl, and divergence of vector fields. For a differential form \( \omega \), the exterior derivative \( d\omega \) produces a new form of one higher degree. For example, if \( \omega \) is a 1-form, then \( d\omega \) is a 2-form. The exterior derivative satisfies \( d^2 = 0 \), meaning that applying it twice yields zero, which is analogous to the fact that the curl of the gradient is zero.

Can you give an example of a physical application of differential forms?

One prominent example is in electromagnetism. The electromagnetic field can be described by a 2-form \( F \) on spacetime. Maxwell's equations can be compactly written using differential forms: \( dF = 0 \) and \( d*F = J \), where \( * \) is the Hodge star operator and \( J \) is the current 3-form. This formulation is coordinate-independent and elegantly

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