Numerical Study of Induced False Vacuum Decay at High Energies

We calculate numerically the probability $\exp[ {1\over\lambda} F(E/E_{sph},N/N_{sph})]$ of the false vacuum decay in the massive four-dimensional $-\lambda\phi^4$ model from multiparticle initial states with fixed number of particles $N$ and energy $E$ greater than the height of the barrier $E_{sph}$. We find that at $E\lsim 3E_{sph}$ and $N\lsim 0.4N_{sph}$ the decay is classically forbidden and thus is exponentially suppressed. We argue that the classically forbidden region extends at small $N$ at least up to $E\sim 10 E_{sph}$ and, most likely, to all energies. Our data suggest that the false vacuum decay induced by two-particle collisions is exponentially suppressed at all energies.