Abstract :
We show how parametric resonance mechanism follows quench mechanism in the classical linear sigma model. The parametric resonance amplifies long wavelength modes of the pion for more than 10 fm/c. The shifting from the quench mechanism to the parametric resonance mechanism is described by a time dependent quantity. After the quench mechanism is over, that quantity has an oscillating part, which causes the parametric resonance. Since its frequency is 2mπ (mπ: pion mass), very long wavelength modes such as k=40 MeV of the pion are amplified by the parametric resonance.
