LeviCivita in Orthogonal Curvilinear Coordinate System: "Cross Product Matrix

In summary, the matrices that make up the Levi Civita 3x3x3 matrix remain the same regardless of the coordinate system, as stated in the Levi-Civita symbol article. However, note that this only holds true for coordinate systems where the basis of the tangent space is orthonormal with respect to the metric and matches a selected orientation. This is not the case for spherical coordinates, where the basis is orthogonal but not orthonormal. Therefore, in order to generate the 3x3x3 matrix for spherical coordinates, one must use the normalized spherical unit vectors instead of the regular basis vectors.
  • #1
ltkach2015
37
1
If given a position vector defined for a orthogonal curvilinear coordinate system HOW would the matrices that make up the Levi Civita 3x3x3 matrix remain the same?

"Levi Civita 3x3x3 is said to be independent of any coordinate system or metric tensor"(https://en.wikipedia.org/wiki/Levi-Civita_symbol)Position Vector in a cartesian coordinate system
R =
[x;y;z] = x*i + y*j + z*k = x*[1;0;0] + y*[0;1;0] + z*[0;0;1]
Cartesian Unit Vectors
i = [1;0;0], j = [0;1;0], k = [0;0;1]
Angular Velocity Vector
w =
[w1;w2;w3]
Velocity Vector
V =
cross(w,R) = w x R = CPM(w)*R
Cross Product Matrix (CPM) Derivation

Matrices that make up each 'page' of the 3x3x3 alternating tensor/symbol/Levi-Civita symbol
I = j*transpose(k) - k*transpose(j) = [0 0 0; 0 0 1; 0 -1 0]
J = -(i*transpose(k) - k*transpose(i)) = [0 0 -1; 0 0 0; 1 0 0]
K = i*transpose(j) - j*transpose(i) = [0 1 0; -1 0 0; 0 0 0]​

LeviCivita here is a 3x3x3 matrix
LeviCivita(all rows, all columns, page1) = I
LeviCivita(all rows, all columns, page2) = J
LeviCivita(all rows, all columns, page3) = K

CPM = transpose(w)*LeviCivita
= [transpose(w)*LeviCivita(all rows, all columns, page1) ; transpose(w)*LeviCivita(all rows, all columns, page2); ...transpose(w)*LeviCivita(all rows, all columns, page3) ]
= [transpose(w)*I ; transpose(w)*J ; transpose(w)*K ]​

[ 0 -w3 w2 ]
[ w3 0 -w1 ] = CPM(w)
[ -w2 w1 0 ]


And, as expected V = w x R = CPM(w)*R = [w2*z - w3*y; w3*x - w1*z; w1*y - w2*x]

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Again how would the Levi Civita 3x3x3 matrix remain the same in an orthogonal curvilinear coordinate system?

For example given the position vector defined in spherical coordinates. Coordinates: r = radius, o = theta, p = phi
R = [r*cos(o)*sin(p); r*sin(o)*sin(p); r*cos(p)] = r*normalized_r
normalized_r
is the normalized unit vector for the r direction​

Should one assume the following to arrive at the matrices that form the Levi Civita symbol:
r = o*transpose(p) - o*transpose(p)
o = -(r*transpose(p) - p*transpose(r))
p = r*transpose(o) - o*transpose(r)​

where the unit vectors are found from:
r = gradient(x) = [partial_dx/partial_dr; partial_dx/partial_do; partial_dx/partial_dp]
o = gradient(y) = [partial_dy/partial_dr; partial_dy/partial_do; partial_dy/partial_dp]
p = gradient(z) = [partial_dz/partial_dr; partial_dz/partial_do; partial_dz/partial_dp]OR Should one use the normalized unit vectors to form the matrices instead?
r = normalized_o*transpose(normalized_p) - normalized_o*transpose(normalized_o)
o = -(normalized_r*transpose(normalized_p) - normalized_p*transpose(normalized_r))
p = normalized_r*transpose(normalized_o) - normalized_o*transpose(normalized_r)
None of these resulted in the matrices that comprised the Levi Civita 3x3x3 matrix.

This spherical coordinate system is not right handed. Should one change the order from r, o, p to r, p, o?
https://math.stackexchange.com/ques...lculating-dot-and-cross-products-in-spherical
 
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  • #2
ltkach2015 said:
If given a position vector defined for a orthogonal curvilinear coordinate system HOW would the matrices that make up the Levi Civita 3x3x3 matrix remain the same?
From where in the linked wiki article was this statement taken?

If it's from the section entitled Levi-Civita Tensors then note needs to be taken of the qualification stated that the agreement holds only 'wherever the coordinate system is such that the basis of the tangent space is orthonormal with respect to the metric and matches a selected orientation.'

IIRC the basis of the tangent space that arises from spherical coordinates is orthogonal but not orthonormal.
 
  • #3
andrewkirk said:
From where in the linked wiki article was this statement taken?

If it's from the section entitled Levi-Civita Tensors then note needs to be taken of the qualification stated that the agreement holds only 'wherever the coordinate system is such that the basis of the tangent space is orthonormal with respect to the metric and matches a selected orientation.'

IIRC the basis of the tangent space that arises from spherical coordinates is orthogonal but not orthonormal.

I am not following.

I should have said: assuming that the Levi Civita 3x3x3 matrix would have to remain the same for orthogonal curvilinear coordinates. That's my own thought as I knew I had to somehow generate the same velocity vector. And I think the article confirms my thinking; I quoted it in the beginning of my post: "Levi-Civita symbol are independent of any metric tensor and coordinate system"

But if that's the case how do I get those matrices that form the 3x3x3 for spherical coordinates?

Should I use the normalized spherical unit vectors to generate that 3x3x3? As spherical is orthogonal and not orthonormal.
 

What is the Levi-Civita symbol in orthogonal curvilinear coordinate systems?

The Levi-Civita symbol is a mathematical tool used to represent the orientations of coordinate systems in three-dimensional space. It takes on a value of +1, -1, or 0 depending on the order of the indices and the permutation of the coordinate axes.

How is the Levi-Civita symbol used in calculating the cross product in orthogonal curvilinear coordinate systems?

The Levi-Civita symbol is used to construct the cross product matrix, which is then multiplied by the vectors in the cross product formula. This allows for the calculation of the cross product in orthogonal curvilinear coordinate systems.

What is a cross product matrix and how is it related to the Levi-Civita symbol?

A cross product matrix is a 3x3 matrix used in the calculation of the cross product in orthogonal curvilinear coordinate systems. It is constructed using the Levi-Civita symbol, with the values of the matrix dependent on the orientation of the coordinate axes.

What is the significance of the Levi-Civita symbol in physics and engineering?

The Levi-Civita symbol is used in many areas of physics and engineering, including mechanics, electromagnetism, and fluid dynamics. It allows for the calculation of quantities such as torque, angular momentum, and vorticity in different coordinate systems.

Are there any limitations to using the Levi-Civita symbol in orthogonal curvilinear coordinate systems?

One limitation to using the Levi-Civita symbol is that it only applies to three-dimensional space. Additionally, it can only be used in orthogonal curvilinear coordinate systems, and not in non-orthogonal systems or higher dimensions.

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