Every particle in the universe has been, at a given point of its history, interacting with other particles. So, how is it possible to decide whether a given particle can be treated as an isolated quantum system the states of which are vectors of a single Hilbert space? Altenatively, what...
I have a question about the gravitational model used to describe tides:
Is it correct to simply add the tide potentials respectively due to Earth and sun as most people do? (see for instance a good example of this approach in Eq 9 of: http://arxiv.org/PS_cache/physics/pdf/0701/0701301v1.pdf)...