Recent content by Orodruin

  1. Orodruin

    I Parallel transport

    The Levi-Civita connection is the unique metric compatible and torsion free connection on a Riemannian manifold (or pseudo-Riemannian). In general a connection has nothing to do with any basis, although its connection coefficients can be expressed in it. The Levi-Civita connection is...
  2. Orodruin

    I Parallel transport

    Parallel transport is perfectly well defined along non-geodesic curves. The manifold described in the video is a Riemannian manifold so there is no need to define (or use for) a Fermi-Walker transport.
  3. Orodruin

    I Parallel transport

    No, definitely not. There should be no outside reference. If he walks straight forward, he keeps the arrow in the same direction relative to himself. If he walks in a curved path, he needs to adjust the arrow accordingly when he turns. No, see above. No.
  4. Orodruin

    Errors and significant figures

    This is only correct if you view ##\Delta L## and ##\Delta B## as fixed numbers. In a setting where you have estimated errors, it is more appropriate to view them as statistical distributions, normally Gaussian distributions. If these are uncorrelated then you would obtain the result with the...
  5. Orodruin

    I Follow-up on the Expanding Universe Insight article

    They are the same to the ordered considered in the ##\simeq## relation.
  6. Orodruin

    Tension in a string connecting two blocks having equal and opposite velocities

    The problem statement also states different masses with the same velocity. So we have to go with that? But those two are incompatible. As stated, something in the problem statement needs to be corrected. The simplest change is striking out the y in ”any”, but we simply cannot know what was the...
  7. Orodruin

    A Decomposition into irreps of compact Lie group

    I think I found my issue. I was trying ##\sin^2(\theta)##, but when mapping from SU(2) to SO(3), the ##t## here is actually ##\theta/2##? Using ##\sin^2(\theta)## I obtained that the fundamental representation should contain the trivial one once, which would be absurd. Using...
  8. Orodruin

    A Decomposition into irreps of compact Lie group

    When decomposing a representation ##\rho## of a finite group ##G## into irreducible representations, we can find the number of times the representation contains a particular irrep ##\rho_0## through the character inner product $$ \langle \chi, \chi_0\rangle = \frac{1}{|G|} \sum_{g\in G} \chi(g)...
  9. Orodruin

    B Newton's first law?

    For things moving free or at rest, Observe what the first law does best. It defines a key frame, Inertial by name, Where the second law then is expressed. Source: https://www.physics.harvard.edu/undergrad/limericks
  10. Orodruin

    I How to calculate basis vectors from metric tensor (as a matrix)?

    You’ve gotten things wrong. The basis is a choice. The typical coordinate basis depends only on the coordinates chosen - the manifold does not even need to have a metric.
  11. Orodruin

    Can a dipole be modeled as a point charge?

    Your post seemed to indicate otherwise …
  12. Orodruin

    Can a dipole be modeled as a point charge?

    This dependence is present also far away from the dipole.
  13. Orodruin

    Independent components of three indexed systems ##T_{ijk}##

    There is no need to split into cases as you do. The third index is just an additional copy of the 2-index system for every possible value of the index as compared to the basic 2-index systems you mentioned. It follows directly that the symmetric case is 3x6 = 18 and the anti-symmetric 3x3 = 9.
  14. Orodruin

    Flux through a cylindrical surface enclosing part of a sphere

    Hint: You don’t need to compute the flux integral. Edit: with the dimensions of A, the cylinder does not completely enclose the sphere. The cylinder radius is too small.
Back
Top