arXiv subjects

Sören Schweers

Publications and source records attributed to Sören Schweers.

7 recordsLinked to original sources

arXiv2026

Current reversals in driven lattice gases and Brownian motion

Particle currents flowing against an external driving are a fascinating phenomenon in both single-particle and interacting many-particle systems. Underlying physical mechanisms of such current reversals are not fully understood yet. Predicting their appearance is difficult, in particular for interaction-induced ones that emerge upon changes of the particle density. We here derive conditions on external time-dependent drivings, under which current reversals occur in lattice gases with arbitrary pair interactions. Our derivation is based on particle-hole symmetry and shows that current reversals must emerge if the time-varying driving potential changes sign after a translation in time and/or space. Our treatment includes nonstationary dynamics and time-dependent spatially averaged currents in nonequilibrium steady states. It gives insight also into possible occurrences of current reversals in continuous-space dynamics, which we demonstrate for hardcore interacting particles driven across a periodic potential by a traveling wave.

cond-mat.stat-mech↗

arXiv2025

Nonequilibrium phase transition in single-file transport at high crowding

Driven particle transport in crowded and confining environments is fundamental to diverse phenomena across physics, chemistry, and biology. A main objective in studying such systems is to identify novel emergent states and phases of collective dynamics. Here, we report on a nonequilibrium phase transition occurring in periodic structures at high particle densities. This transition separates a weak-current phase of thermally activated transport from a high-current phase of solitary wave propagation. It is reflected also in a change of universality classes characterizing correlations of particle current fluctuations. Our findings demonstrate that sudden changes to high current states can occur when increasing particle densities beyond critical values.

cond-mat.stat-mech↗

arXiv2025

Correlations of density and current fluctuations in single-file motion of hard spheres and in driven lattice gas with nearest-neighbor interaction

We analyze correlations between density fluctuations and between current fluctuations in a one-dimensional driven lattice gas with repulsive nearest-neighbor interaction and in single-file Brownian motion of hard spheres dragged across a cosine potential with constant force. By extensive kinetic Monte Carlo and Brownian dynamics simulations we show that density and current correlation functions in nonequilibrium steady states follow the scaling behavior of the Kardar-Parisi-Zhang (KPZ) universality class. In a coordinate frame comoving with the collective particle velocity, the current correlation function decays as $\sim -t^{-4/3}$ with time $t$. Density fluctuations spread superdiffusively as $\sim t^{2/3}$ at long times and their spatio-temporal behavior is well described by the KPZ scaling function. In the absence of the cosine potential, the correlation functions in the system of dragged hard spheres show scaling behavior according to the Edwards-Wilkinson universality class. In the coordinate frame comoving with the mean particle velocity, they behave as in equilibrium, with current correlations decaying as $\sim -t^{-3/2}$ and density fluctuations spreading diffusively as $\sim t^{1/2}$.

cond-mat.stat-mech↗

arXiv2024

Fast Brownian cluster dynamics

We present an efficient method to perform overdamped Brownian dynamics simulations in external force fields and for particle interactions that include a hardcore part. The method applies to particle motion in one dimension, where it is possible to update particle positions by repositioning particle clusters as a whole. These clusters consist of several particles in contact. They form because particle collisions are treated as completely inelastic rather than elastic ones. Updating of cluster positions in time steps is carried out by cluster fragmentation and merging procedures. The presented method is particularly powerful at high collision rates in densely crowded systems, where collective movements of particle assemblies is governing the dynamics. As an application, we simulate the single-file diffusion of sticky hard spheres in a periodic potential.

cond-mat.stat-mech↗

arXiv2023

Weak pinning and long-range anticorrelated motion of phase boundaries in driven diffusive systems

We show that domain walls separating coexisting extremal current phases in driven diffusive systems exhibit complex stochastic dynamics, with a subdiffusive temporal growth of position fluctuations due to long-range anticorrelated current fluctuations and a weak pinning at long times. This weak pinning manifests itself in a saturated width of the domain wall position fluctuations that increases sublinearly with the system size. As a function of time $t$ and system size $L$, the width $w(t,L)$ exhibits a scaling behavior $w(t,L)=L^{3/4}f(t/L^{9/4})$, with $f(u)$ constant for $u\gg1$ and $f(u)\sim u^{1/3}$ for $u\ll1$. An Orstein-Uhlenbeck process with long-range anticorrelated noise is shown to capture this scaling behavior. Results for the drift coefficient of the domain wall motion point to memory effects in its dynamics.

cond-mat.stat-mech↗

arXiv2023

Scaling laws for single-file diffusion of adhesive particles

Single-file diffusion refers to the Brownian motion in narrow channels where particles cannot pass each other. In such processes, the diffusion of a tagged particle is typically normal at short times and becomes subdiffusive at long times. For hard-sphere interparticle interaction, the time-dependent mean squared displacement of a tracer is well understood. Here we develop a scaling theory for adhesive particles. It provides a full description of the time-dependent diffusive behavior with a scaling function that depends on an effective strength of adhesive interaction. Particle clustering induced by the adhesive interaction slows down the diffusion at short times, while it enhances subdiffusion at long times. The enhancement effect can be quantified in measurements irrespective of how tagged particles are injected into the system. Combined effects of pore structure and particle adhesiveness should speed up translocation of molecules through narrow pores.

cond-mat.stat-mech↗

arXiv2022

Brownian dynamics simulations of hard rods in external fields and with contact interactions

We propose a simulation method for Brownian dynamics of hard rods in one dimension for arbitrary continuous external force fields. It is an event-driven procedure based on the fragmentation and mergers of clusters formed by particles in contact. It allows one to treat particle interactions in addition to the hard-sphere exclusion as long as the corresponding interaction forces are continuous functions of the particle coordinates. We furthermore develop a treatment of sticky hard spheres as described by Baxter's contact interaction potential.

cond-mat.stat-mech↗