Presentation on theme: "Time-dependent picture for trapping of an anomalous massive system into a metastable well Jing-Dong Bao Department of Physics, Beijing."— Presentation transcript:
Time-dependent picture for trapping of an anomalous massive system into a metastable well Jing-Dong Bao Department of Physics, Beijing Normal University – 21 Beijing
1. The scale theory 2. Barrier passage dynamics 3. Overshooting and backflow 4. Survival probability in a metastable well
1. The model (anomalous diffusion) ground state saddle exit A metastable potential:
What is an anomalous massive system? (i) The generalized Langevin equation Here we consider non-Ohmic model （ ） (ii) the fractional Langevin equation Jing-Dong Bao, Yi-Zhong Zhuo: Phys. Rev. C 67, (2003). J. D. Bao, Y. Z. Zhuo: Phys. Rev. Lett. 91, (2003). memory effect, underdamped
Jing-Dong Bao, Yan Zhou: Phys. Rev. Lett. 94, (2005). Normal Brownian motion Fractional Brownian motion
Here we add an inverse and anomalous Kramers problem and report some analytical results, i.e., a particle with an initial velocity passing over a saddle point, trapping in the metastable well and then escape out the barrier. The potential applications : (a) Fusion-fission of massive nuclei; (b) Collision of molecular systems; (c) Atomic clusters; (d) Stability of metastable state, etc.
The scale theory (1) At beginning time: the potential is approximated to be an inverse harmonic potential, i.e., a linear GLE; (2) In the scale region (descent from saddle point to ground state), the noise is neglected, i.e., a deterministic equation; (3) Finally, the escape region, the potential around the ground state and saddle point are considered to be two linking harmonic potentials, (also linear GLE).
2. Barrier passage process J. D. Bao, D. Boilley, Nucl. Phys. A 707, 47 (2002). D. Boilley, Y. Abe, J. D. Bao, Eur. Phys. J. A 18, 627 (2004).
The response function is given by
Where is the anomalous fractional constant ; The effective friction constant is written as
The passing probability (fusion probability) over the saddle point is defined by It is also called the characteristic function
s ubdiffusion normal diffusion Passing Probability
3. Overshooting and backflow J. D. Bao, P. Hanggi, to be appeared in Phys. Rev. Lett. (2005) * For instance, quasi-fission mechanism
4. Survival probability in a metastable well We use Langevin Monte Carlo method to simulate the complete process of trapping of a particle into a metastable well 0 x
J.D. Bao et. al., to be appeared in PRE (2005).
Summary 1. The passage barrier is a slow process, which can be described by a subdiffusion; 2. When a system has passed the saddle point, anomalous diffusion makes a part of the distribution back out the barrier again, a negative current is formed; 3. Thermal fluctuation helps the system pass over the saddle point, but it is harmful to the survival of the system in the metastable well.