2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/80119We describe the quantum mechanical spreading of a Gaussian wave packet by means of the semiclassical WKB approximation of Berry and Balazs. We find that the time scale $τ$ on which this approximation breaks down in a chaotic system is larger than the Ehrenfest times considered previously. In one dimension $τ=\fr{7}{6}λ^{-1}\ln(A/\hbar)$, with $λ$ the Lyapunov exponent and $A$ a typical classical action.4 pagesChaotic DynamicsMesoscale and Nanoscale PhysicsQuantum Physicstext