Time-Independent Schrödinger Equation — David J. Griffiths
Physics — Quantum Mechanics · circular_ring
Problem
Imagine a bead of mass m that slides frictionlessly around a circular wire ring of circumference L. (This is just like a free particle, except that ψ(x+L)=ψ(x).) Find the stationary states (with appropriate normalization) and the corresponding allowed energies. Note that there are (with one exception) two independent solutions for each energy En—corresponding to clockwise and counter-clockwise circulation; call them ψn+(x) and ψn−(x). How do you account for this degeneracy, in view of the theorem in Problem 2.44 (why does the theorem fail, in this case)?