Will_Sawin comments on Beyond Statistics 101 - Less Wrong

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

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Comment author: btrettel 27 June 2015 03:40:42PM 1 point [-]

Not familiar with Noether's theorem. Seems useful for constructing models, and perhaps determining if something else beyond mass, momentum, and energy is conserved. Is the converse true as well, i.e., does conservation imply that symmetries exist?

I'm also afraid I know nearly nothing about non-linear stability, so I'm not sure what you're referring to, but it sounds interesting. I'll have to read the Wikipedia page. I'd be interested if you know any other good resources for learning this.

Comment author: Will_Sawin 27 June 2015 09:58:14PM 0 points [-]

Conservation gives a local symmetry but there may not be a global symmetry.

For instance, you can imagine a physical system with no forces at all, so everything is conserved. But there are still some parameters that define the location of the particles. Then the physical system is locally very symmetric, but it may still have some symmetric global structure where the particles are constrained to lie on a surface of nontrivial topology.