Dynamics Of Multiscale Purely Repulsive Interacting Particle System

In recent years,multiscale phenomena have attracted extensive attention of scientists,and then multiscale science has developed rapidly.As a universal phenomenon inherent in the objective world,multiscale phenomena are active in mathematics,physics,fluid mechanics,chemistry,materials science,biology and other disciplines and the intersection between them.In addition,multiscale phenomena also run through the entire discussion of nonlinearity and complexity,and are an important way to study nonequilibrium statistical physics and molecular dynamics.When complex systems emerge in the field of soft matter,people also apply the research on multiscale phenomena to the direction of soft matter.On the one hand,it is used to consider the nonequilibrium problem of the complex system,and on the other hand,it is used to explore the specific mechanism of biological activity and self-organization in soft matter.In fact,the research results in these two aspects have also laid a good foundation for the exploration of the dynamics of multiscale interacting particle systems,and speeded up revealing the origin of biological activity.At present,the research on multiscale phenomena is roughly divided into three aspects,namely the description of multiscale phenomena,the mechanism of multiscale phenomena,and the intrinsic relationship between multiscale phenomena.When studying multiscale phenomena,we must not only understand the different expressions of multi-scale phenomena,but also grasp the mechanism of multiscale,so as to gain insight into the internal correlation of multiscale phenomena.In the cross study of different multiscale phenomena,the selection of appropriate multiscale analyzing methods has also become the key to the research.Molecular dynamics is considered to be an effective method for describing multiscale interacting particle systems.In this thesis,the Langevin molecular dynamics method is used to systematically investigate the dynamics of two-dimensional multiscale purely repulsive interacting particle system on periodically distributed point-like pinning(or obstacle)substrates under active and passive noise(thermal noise)environments.The detailed contents of the thesis are arranged as follows:In the first chapter,we firstly give an overview of the multiparticle system and its nonequilibrium dynamics.Secondly,the multiscale pure repulsive interaction particle system and its research progress are introduced.Finally,the Langevin molecular dynamics simulation method used in this thesis is briefly described.In the second chapter,we use Langevin molecular dynamics to numerically study the dynamics of a two-dimensional(2D)multiscale purely repulsive interacting particle system on a periodic Gaussian pinning substrate under thermal and active noise environments.It is found that the system near the depinning exhibits crystalline-like and stripe structures under thermal noise environments,but the living islands-like structures similar to the active system do not appear.The active noise does not affect the dynamic phase and phase transition above the depinning.In chapter 3,we numerically study the dynamic properties of a 2D multiscale purely repulsive particle system on the periodic laser-optical substrates under thermal and active noise environments using Langevin molecular dynamics.It is found that:for the lower substrate strength,the active noise is larger,leading to stronger correlation between particles,and the particles start to move in small clusters and the system moves as a crystal-like;With the increase of the substrate strength,the particles get rid of the cluster and move as single particles;when the substrate strength is high enough,the clusters are broken when the motion starts,and all the particles move as single particles;under thermal noise,all the particles start to move as single particles.In chapter 4,we give the conclusion and outlook of this thesis.The results of this thesis will provide important guide for exploring the transport of nutrients in the biological environment,the generation mechanism of the ordered state of the dynamic system,and how to control the formation of the dynamic order state by an external field.