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I'm currently learning about Feynman Path Integrals, and I came across the following paragraph:
"Periodic classical orbits will carry a complex phase which will in general average to zero over many orbits. However if the action of a single orbit is 2πh ̄× integer, the phase factor is unity and therefore such orbits will dominate the path integral. This is the Bohr-Sommerfeld quantisation condition."
Why does the action of a single orbit being $2\pi\hbar ̄~\times $ integer make that path dominate the path integral?