Douglas_Knight comments on Beyond Statistics 101 - Less Wrong

19 Post author: JonahSinick 26 June 2015 10:24AM

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Comment author: Vaniver 27 June 2015 02:15:53PM 3 points [-]

This is a great point. Other than fairly easy geometric and time symmetries, do you have any advice or know of any resources which might be helpful towards finding these symmetries?

Are you familiar with Noether's Theorem? It comes up in some explanations of Buckingham pi, but the point is mostly "if you already know that something is symmetric, then something is conserved."

The most similar thing I can think of, in terms of "resources for finding symmetries," might be related to finding Lyapunov stability functions. It seems there's not too much in the way of automated function-finding for arbitrary systems; I've seen at least one automated approach for systems with polynomial dynamics, though.

Comment author: Douglas_Knight 27 June 2015 08:09:33PM *  2 points [-]

Noether's theorem has nothing to do with Buckingham's theorem. Buckingham's theorem is quite general (and vacuous), while Noether's theorem is only about hamiltonian/lagrangian mechanics.

Added: Actually, Buckingham and Noether do have something in common: they both taught at Bryn Mawr.

Comment author: Vaniver 27 June 2015 09:57:52PM 0 points [-]

Noether's theorem has nothing to do with Buckingham's theorem.

Both of them are relevant to the project of exploiting symmetry, and deal with solidifying a mostly understood situation. (You can't apply Buckingham's theorem unless you know all the relevant pieces.) The more practical piece that I had in mind is that someone eager to apply Noether's theorem will need to look for symmetries; they may have found techniques for hunting for symmetries that will be useful in general. It might be worth looking into material that teaches it, not because it itself is directly useful, but because the community that knows it may know other useful things.

Comment author: btrettel 27 June 2015 08:35:28PM *  0 points [-]

In what sense do you mean Buckingham's theorem is vacuous?

Comment author: EHeller 27 June 2015 09:44:18PM 0 points [-]

It's a quite bit more general than Lagrangian mechanics. You can extend it to any functional that takes functions between two manifolds to complex numbers.