Probably off topic: it's the second time I am reading about phase shifts today. The first time I read it was in context of interpretability of attention in transformer neural nets where they find phase shifts between positional and semantic learning: https://arxiv.org/abs/2402.03902
In my mind it is a geometric thing, that is, you find phases in things like oscillators that have the symmetry that the complex numbers do. (e.g. position and momentum for the oscillator rotate around the origin once in every cycle)
this is something that most physical therapists could talk about in-depth, albeit less eloquently.
modifying ϕ (via posture or action) is essentially what is done as a first response to encountering clonus in a patient undergoing assisted physical therapy.
