What is the connection between 2-forms, determinants, and cross products in R^3?

In summary, 2-forms are defined as the wedge product of two 1-forms, which can be represented as a determinant. In R^3, the cross product between two 1-forms can also be expressed as a 2-form. This is related to the determinant and has a geometric interpretation in terms of projection onto different axes. However, this may not hold true for 1-forms in R^2 or other coordinate systems. When considering functions of vectors, they can also be incorporated into the concept of 2-forms.
  • #1
JonnyMaddox
74
1
Hi, 2-forms are defined as

[itex]du^{j} \wedge du^{k}(v,w) = v^{j}w^{k}-v^{k}w^{j} = \begin{vmatrix} du^{j}(v) & du^{j}(w) \\ du^{k}(v) & du^{k}(w) \end{vmatrix}[/itex]

But what if I have two concret 1-forms in [itex]R^{3}[/itex] like [itex](2dx-3dy+dz)\wedge (dx+2dy-dz)[/itex] and then I calculte [itex](2dx-3dy+dz)\wedge (dx+2dy-dz)=-7dy \wedge dx +3dz \wedge dx - dy \wedge dz= 7 dx \wedge dy + 3 dz \wedge dx + dy \wedge dz[/itex] (now a 2-form)
I know this is the same as the cross product between [itex](2,-3,1)^{T}[/itex] and [itex](1,2,-1)^{T}[/itex]
What has this to do with the determinant? If I calculate this for 1-forms in [itex]R^{2}[/itex] like [itex](2dx+4dx)\wedge (3dx+9dy) = -18 dx\wedge dy +12 dx \wedge dy = 6 dx \wedge dy[/itex] which equals the determinant of the vectors [itex](2,4)[/itex] and [itex](3,9)[/itex]. But this is not like 1-forms in [itex]R^{3}[/itex]. And is the geometric interpretation right that [itex]7 dx \wedge dy + 3 dz \wedge dx + dy \wedge dz[/itex] means that 7 is the part of the area projected to the xy axis, 3 the part projecte to the zx axis and 1 the part projected onto the yz axis? Or is it a different coordinate system like dxdy, dzdx and dydz ?
Now actually these are all functions of vectors like [itex]v[/itex] or [itex]w[/itex] as in the definition of 2-forms. What happens if they come into this picture?
 
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  • #2
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FAQ: What is the connection between 2-forms, determinants, and cross products in R^3?

What is a form?

A form is a structure or arrangement of something, often used to describe the physical characteristics of an object or entity.

What are the different types of forms?

There are several types of forms, including geometric forms (such as circles and squares), biological forms (such as plant and animal structures), and linguistic forms (such as words and sentences).

What is a determinant?

A determinant is a mathematical concept used to describe the unique solutions or properties of a system or equation.

How are forms and determinants related?

Forms and determinants are closely related in mathematics, as the determinant of a matrix can be used to determine the properties or characteristics of the form represented by the matrix.

What is the significance of forms and determinants in science?

Forms and determinants are important in a variety of scientific fields, including physics, chemistry, and biology. They can be used to describe and analyze the physical and structural properties of objects and systems, and to make predictions about their behavior.

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