Why Pretty Much Everything is a Harmonic Oscillator

[@danthewalsh]

Thanks for your submission, Bob. Good to see you're still working on valuable physics problems. Good, also, to see that the ranking system for SoME2 is even bringing relatively small channels (at the time of writing, 63 views) to my attention. Hope all is well, and keep up the good work!

[@danthewalsh]

Might be useful to note that it is possible for the quadratic term in your Taylor expansion to also be zero, in which case we'd want to look at the cubic term. If we want this point to be a stable equilibrium, we'd require this term to be zero also, so we'd want to look at the quartic term. In this example, the small-amplitude solution would not resemble a harmonic oscillator. Incidentally, we know such "phi^4" terms do get considered as perturbations in QFT, although they're usually still starting from a harmonic theory like the Klein Gordon equation.

[@celestineP]

Thank you for this video. It would help if you could provide timestamps to different sections of the video (so people familiar with the topic could skip to the novel bits in this 30 min long video).