Non-Gaussian Fluctuation and Non-Markovian Effect in the Nuclear Fusion Process: Langevin Dynamics Emerging from Quantum Molecular Dynamics Simulations

TL;DR

This paper investigates the complex stochastic dynamics of nuclear fusion near the Coulomb barrier, revealing non-Gaussian and non-Markovian effects through quantum molecular dynamics simulations, and models them with a generalized Langevin equation.

Contribution

It demonstrates how microscopic nucleon dynamics lead to non-Gaussian and non-Markovian fluctuations in the fusion process, advancing the modeling with a generalized Langevin approach.

Findings

Non-Gaussian distribution of the random force causes dissipation dynamics.

Large friction coefficient and strong time correlations are observed inside the Coulomb barrier.

Emergent fusion dynamics can be effectively described by a generalized Langevin equation with memory.

Abstract

Macroscopic parameters as well as precise information on the random force characterizing the Langevin type description of the nuclear fusion process around the Coulomb barrier are extracted from the microscopic dynamics of individual nucleons by exploiting the numerical simulation of the improved quantum molecular dynamics. It turns out that the dissipation dynamics of the relative motion between two fusing nuclei is caused by a non-Gaussian distribution of the random force. We find that the friction coefficient as well as the time correlation function of the random force takes particularly large values in a region a little bit inside of the Coulomb barrier. A clear non-Markovian effect is observed in the time correlation function of the random force. It is further shown that an emergent dynamics of the fusion process can be described by the generalized Langevin equation with memory effects by appropriately incorporating the microscopic information of individual nucleons through the random force and its time correlation function.