Physics Cup – TalTech 2021 – Pr. 4, Hint 1.

It will help if you learn about adiabatic invariants, cf. the material from the IPhO-2012 web page. Keep in mind that while in general, an adiabatic invariant is conserved by a slowly evolving potential, it is not conserved during separatrix crossing (when the phase trajectory is crossing a separatrix so that the area of a new loop is added to the existing adiabatic invariant).

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