I have heard on various occasions that the Hamiltonian/Lagrangian of the Hydrogen atom or that of a particle moving in $1/r$-potential can be transformed into that of a free particle moving on the surface of a three-dimensional sphere embedded in a four-dimensional space. Is this easy to show?
There seems to be a paper by Fock given in citation [10] Laplace–Runge–Lenz vector (at Wikipedia) but unfortunately it is not in English. Is anyone aware of the content of this paper, Zur Theorie des Wasserstoffatoms?