Eigenvalues of the Frenet formulas and angular velocity

In summary, the book states that the nonzero eigenvalue of K^2, where K is the matrix given in the Frenet-Serret formulas, is -\alpha^2. This can be verified by computing the eigenvalues of K, but it is also known without computation.
  • #1
ForMyThunder
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So there's a circular helix parametrized by [tex]\vec x(t)=(a\cos(\alpha t), a\sin(\alpha t), bt)[/tex] and you have the matrix [tex]K[/tex] given in the Frenet-Serret formulas. In the book I'm reading it says that [tex]-\alpha^2[/tex] is the nonzero eigenvalue of [tex]K^2[/tex]. Can someone explain how they know this is? I understand that you can compute the eigenvalues of the matrix to verify this but how can you say this without computation?
 
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  • #2
ForMyThunder said:
So there's a circular helix parametrized by [tex]\vec x(t)=(a\cos(\alpha t), a\sin(\alpha t), bt)[/tex] and you have the matrix [tex]K[/tex] given in the Frenet-Serret formulas. In the book I'm reading it says that [tex]-\alpha^2[/tex] is the nonzero eigenvalue of [tex]K^2[/tex]. Can someone explain how they know this is? I understand that you can compute the eigenvalues of the matrix to verify this but how can you say this without computation?

Can you show me why the eigen value is -alpha^2?

I get +-alpha^2/(a.alpha^2 + b^2)
 

1. What are eigenvalues of the Frenet formulas and angular velocity?

Eigenvalues refer to the special values of a matrix or linear transformation that when multiplied with a vector, give a scalar multiple of that vector. In the context of Frenet formulas and angular velocity, eigenvalues are used to represent the curvature and torsion of a curve in three-dimensional space.

2. How are eigenvalues related to the Frenet formulas and angular velocity?

Eigenvalues are used in the Frenet formulas to determine the curvature and torsion of a curve, while angular velocity is a vector quantity that represents the rate of change of orientation of a rotating body. These concepts are related because the eigenvalues of the Frenet formulas can be used to calculate the angular velocity of a curve.

3. What is the significance of eigenvalues in understanding the behavior of curves?

Eigenvalues play a crucial role in understanding the behavior of curves because they provide information about the curvature and torsion of a curve at any given point. This allows for a more precise and comprehensive understanding of the shape and orientation of a curve, which is useful in various fields such as physics, engineering, and computer graphics.

4. How are eigenvalues and eigenvectors used to calculate the Frenet formulas and angular velocity?

Eigenvalues and eigenvectors are used in the diagonalization process of the Frenet formulas matrix, which allows for the calculation of the curvature and torsion of a curve. The eigenvectors represent the principal directions of the curve, while the eigenvalues represent the associated principal curvatures and torsions.

5. Can eigenvalues of the Frenet formulas and angular velocity be negative?

Yes, eigenvalues of the Frenet formulas and angular velocity can be negative. Negative eigenvalues indicate that the curve is bending in the opposite direction of the corresponding eigenvector. This is important in understanding the overall shape and behavior of a curve, as it can indicate whether the curve is convex or concave at a certain point.

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