QUANTUM DECAY-RATE OF A NONLINEAR DISSIPATIVE SYSTEM WITH FISSION-LIKE POTENTIAL NEAR T-C

We use a thermodynamic scheme (imaginary free energy method) in terms of the path integral technique to study the quantum decay rates of a m etastable state system coupled to a heat bath in the crossover tempera ture (T-c) region. In this region the transition between thermally act ivated decay and tunneling occurs. A nonlinear coupling form factor is used to overcome the divergent integral in the partition function nea r T-c. The decay rate formula based on the steepest descent approximat ion has been improved. A method is developed to calculate the real and imaginary parts of the partition function which combines a random wal k method with fast-Fourier transform Monte-Carlo evaluation. For a non linear dissipative system with a damping correlation kernel of exponen tial form, the accurate numerical calculations are presented. The effe cts of nonlinear and frequency-dependent damping on the rate are shown .