arXiv subjects

Kristian Stølevik Olsen

Publications and source records attributed to Kristian Stølevik Olsen.

24 records · Page 2Linked to original sources

arXiv2023

Steady-state moments under resetting to a distribution

The non-equilibrium steady states emerging from stochastic resetting to a distribution is studied. We show that for a range of processes, the steady-state moments can be expressed as a linear combination of the moments of the distribution of resetting positions. The coefficients of this series are universal in the sense that they do not depend on the resetting distribution, only underlying dynamics. We consider the case of a Brownian particle and a run-and-tumble particle confined in a harmonic potential, where we derive explicit closed-form expressions for all moments for any resetting distribution. Numerical simulations are used to verify the results, showing excellent agreement.

cond-mat.stat-mech↗

arXiv2022

Entropy production of resetting processes

Stochastic systems that undergo random restarts to their initial state have been widely investigated in recent years, both theoretically and in experiments. Oftentimes, however, resetting to a fixed state is impossible due to thermal noise or other limitations. As a result, the system configuration after a resetting event is random. Here, we consider such a resetting protocol for an overdamped Brownian particle in a confining potential $V(x)$. We assume that the position of the particle is reset at a constant rate to a random location $x$, drawn from a distribution $p_R(x)$. To investigate the thermodynamic cost of resetting, we study the stochastic entropy production $S_{\rm Total}$. We derive a general expression for the average entropy production for any $V(x)$, and the full distribution $P(S_{\rm Total}|t)$ of the entropy production for $V(x)=0$. At late times, we show that this distribution assumes the large-deviation form $P(S_{\rm Total}|t)\sim \exp\left[-t^{2α-1}ϕ\left(\left(S_{\rm Total}-\langle S_{\rm Total}\rangle\right)/t^α\right)\right]$, with $1/2<α\leq 1$. We compute the rate function $ϕ(z)$ and the exponent $α$ for exponential and Gaussian resetting distributions. In the latter case, we find the anomalous exponent $α=2/3$ and show that $ϕ(z)$ has a first-order singularity at a critical value of $z$, corresponding to a real-space condensation transition.

cond-mat.stat-mech↗

arXiv2022

Trapping of active Brownian and run-and-tumble particles: a first-passage time approach

We use a first-passage time approach to study the statistics of the trapping times induced by persistent motion of active particles colliding with flat boundaries. The angular first-passage time distribution and mean first-passage time is calculated exactly for active Brownian and run-and-tumble particles and the results are compared. Theoretical predictions are in excellent agreement with Langevin simulations. Our results shed further light onto how active particles with different dynamics may be equivalent in the bulk, yet behave differently near boundaries or obstacles.

cond-mat.stat-mech↗

arXiv2022

Collective states of active matter with stochastic reversals: emergent chiral states and spontaneous current switching

We study collective dynamical behavior of active particles with topological interactions and directional reversals. Surprising phenomena are shown to emerge as the interaction relaxation time is varied relative to the reversal rate, such as spontaneous formation of collective chiral states due to phase synchronization, and collective directional reversals in the presence of confinement. The results have a direct relevance to modelling and understanding collective reversals and synchronization phenomena in active matter.

cond-mat.soft↗

arXiv2021

Diffusion of active particles with angular velocity reversal

Biological and synthetic microswimmers display a wide range of swimming trajectories depending on driving forces and torques. In this paper we consider a simple overdamped model of self-propelled particles with a constant self-propulsion speed, but an angular velocity that varies in time. Specifically, we consider the case of both deterministic and stochastic angular velocity reversal, mimicking several synthetic active matter systems like propelled droplets. The orientational correlation function and effective diffusivity is studied using Langevin dynamics simulations and perturbative methods.

cond-mat.stat-mech↗

arXiv2020

The escape problem for active particles confined to a disc

We study the escape problem for interacting, self-propelled particles confined to a disc, where particles can exit through one open slot on the circumference. Within a minimal 2D Vicsek model, we numerically study the statistics of escape events when the self-propelled particles can be in a flocking state. We show that while an exponential survival probability is characteristic for non-interaction self-propelled particles at all times, the interacting particles have an initial exponential phase crossing over to a sub-exponential late-time behavior. We propose a new phenomenological model based on non-stationary Poisson processes which includes the Allee effect to explain this sub-exponential trend and perform numerical simulations for various noise intensities.

cond-mat.stat-mech↗