arXiv subjects

Alexander P. Antonov

Publications and source records attributed to Alexander P. Antonov.

At least 19 recordsLinked to original sources

arXiv2026

Critical escape dynamics of an active particle moving on curved surfaces

On the macroscopic scale, active (self-propelled) objects moving through complex environments are often subject to effects arising from both the curvature of the surrounding surface and external influences such as gravity. We study the Kramers escape problem for active Brownian particles in two settings: motion in an external potential driven solely by gradient forces, and motion on a curved manifold subject to an additional constant gravitational force. In the absence of translational noise, a sharp dynamical transition occurs when the self-propulsion velocity $v_0$ reaches a critical velocity $v_c$ required for an escape. Above this threshold, the escape rate $k$ follows a universal scaling form, $k \propto \exp\left[-\mathrm{const}(v_0-v_c)^{-γ}\right]$, with an exponent $γ=3/2$ for the escape in a potential and $γ=1/2$ for the escape on a curved manifold in the presence of gravity. These distinct exponents reveal how the interplay of activity, surface curvature, and gravity determines the critical escape dynamics. Our theoretical predictions are verified by numerical simulations.

cond-mat.stat-mech↗

arXiv2026

Anomalous Mean-Squared Displacement in Quantum Active Matter from a Wigner Phase-Space Framework

Active matter is driven out of equilibrium by a local influx of energy. While classical active matter has been extensively studied, the extension of active matter concepts to quantum systems has been explored far less. In this work we develop a quantum description based on the Wigner function for a quantum system influenced by a classical noise. For the model considered here, the hybrid dynamics reduces to an Ornstein--Uhlenbeck process, enabling us to compute the quantum mean-squared displacement (MSD) using established techniques from classical active matter. We analytically derive the time dependence of the MSD and clarify the conditions under which the characteristic scaling with time MSD $t^6$ emerges, namely the regime of long persistence time and large active noise strength. We also show that, for certain parameter and initial conditions, the MSD can exhibit an even steeper scaling regime MSD $t^7$. In addition, explicit expressions are derived that precisely predict the onset times of $t^6$ and $t^7$ scaling behaviors. Finally, we examine the robustness of these behaviors against quantum fluctuations of the initial state.

cond-mat.soft↗

arXiv2026

Jerky Motion of Active Granular Particles

Abrupt transitions between rest and motion can render the standard Newtonian description -- based on position, velocity, and acceleration -- incomplete, requiring higher-order derivatives such as the jerk, the third time derivative of position. Here, we show that the interplay between activity and dry friction gives rise to robust jerk-dominated dynamics in self-propelled particles: the particle speed increases quadratically with time under an active force, in contrast to the linear growth expected for conventional Newtonian dynamics. We demonstrate this behavior analytically, numerically, and experimentally using active vibrobots self-propelling on a vertically vibrating plate at low vibration amplitudes, where surface asperities generate dry friction and, thus, give rise to jerky motion when combined with activity. Our results establish dry friction as a simple mechanism for realizing higher-order dynamics in active matter and suggest that jerky dynamics may arise broadly in nonequilibrium systems with frictional contacts.

cond-mat.soft↗

arXiv2026

Quantization of the classical Mpemba effect

The Mpemba effect refers to the counterintuitive phenomenon that an initially hot system can freeze faster than an initially warm one. Recent years have brought major advances in both classical and quantum realizations, with the asymmetric bistable potential emerging as the paradigmatic classical benchmark because its mechanism is especially transparent and controllable. Yet for precisely this benchmark problem, the impact of quantization remains unexplored. Here we show that quantization shifts Mpemba behavior to qualitatively new regimes, moving it to ultra-cold temperatures that are orders of magnitude lower than those relevant for classical thermal barrier crossing. In addition, quantization produces inverse and double inverse Mpemba effects that are absent in the corresponding classical dynamics. Our results establish quantization as a robust route to quantum-enabled Mpemba effects inaccessible in classical regimes.

quant-ph↗

arXiv2026

Modeling dissipation in quantum active matter

Active matter is characterized by a constant influx and dissipation of energy that gives rise to directed motion. Dissipation requires interactions with an external environment, such that extending the paradigm of active matter to a quantum framework requires an appropriate description of this environment. In this work, we consider a driven quantum particle undergoing noise and dissipation, with external driving exhibiting characteristics of classical activity. We model the non-unitary dynamics with time-local master equations and analyze the particle motion at different time scales for different forms of the master equations, satisfying different criteria. We systematically compare predictions on the dynamics of particle trajectories and thereby we uncover how the particle motion evolves under the interplay of quantum effects, dissipation, and active-like dynamics. These results are essential for guiding possible experiments aimed at realizing quantum analogues of classical active systems.

quant-ph↗

arXiv2026

A particle-resolved rheological study of chirality transfer and odd transport

Chirality, or the breaking of mirror symmetry, appears across all scales in nature, from molecular conformations to the dynamics of bacterial collectives. Environments composed of such symmetry-breaking constituents can give rise to emergent physical phenomena, particularly in the transport and response of embedded tracers. Yet it remains unclear how chiral environments influence such tracers and through which microscopic mechanisms anomalous responses emerge. Here, we present a particle-resolved study of these systems, demonstrating chirality transfer and odd transport of an object embedded in a chiral active bath. In a rheological experiment, a symmetric passive tracer is driven through collisions with the particles of a non-equilibrium chiral bath. Combining table-top experiments, many-body simulations, and a reduced coarse-grained theory, we demonstrate that local collisions transfer chiral active dynamics to the tracer, which displays circular trajectories. We show that the same mechanism gives rise to a systematic transverse drift under a constant pulling force. Crucially, we identify nonlinear friction as an essential factor that rectifies these transferred chiral active fluctuations into a macroscopic odd response. Our results reveal a microscopic mechanism for odd transport in chiral active matter and provide general insights into transverse transport in driven non-equilibrium systems.

cond-mat.stat-mech↗

arXiv2026

Temperature overshooting in the Mpemba effect of frictional active matter

The traditional Mpemba effect refers to an anomalous cooling phenomenon when an initial hotter system cools down faster than an initial warm system. Such counterintuitive behavior has been confirmed and explored across phase transitions in condensed matter systems and also for colloidal particles exposed to a double-well potential. Here we predict a frictional Mpemba effect for a macroscopic body moving actively on a surface governed by Coulomb (dry) friction. For an initial high temperature, relaxation towards a cold state occurs much faster than that for an intermediate initial temperature, due to a large temperature overshooting in the latter case. This frictional Mpemba effect can be exploited to steer the motion of robots and granules.

cond-mat.soft↗

arXiv2025

Circling crystals in chiral active matter with self-alignment

We study a crystal composed of active units governed by self-alignment and chirality. The first mechanism acts as an effective torque that aligns the particle orientation with its velocity, while the second drives individual particles along circular orbits. We find that even a weak degree of chirality, when coupled with self-alignment, induces collective motion of the entire crystal along circular trajectories in space. We refer to this phase as a circling crystal. When chirality outweigh self-alignment, the circular global motion is suppressed in favor of vortex-like regions of coordinated motion. This state is characterized by oscillating spatial velocity correlations, a power law decay of the energy spectrum, and oscillatory temporal correlations. Our findings can be tested experimentally in systems ranging from epithelial tissues to swarming robots, governed by chirality and self-alignment.

cond-mat.soft↗

arXiv2025

Engineering active motion in quantum matter

We introduce a framework for engineering active quantum matter that involves mimicking the role of self-propulsion through an external trapping potential that is moving along imposed trajectories traced by classical active dynamics. This approach in the presence of dissipation, not only recovers essential dynamical behavior of classical activity, including the ballistic to diffusive cross-over of its mean-square displacement, but also reveals additional features of activity that are of quantum origin. These quantum-active features are revealed in non-dissipative systems, and manifest as novel exponents of the mean-square displacement at short timescales.

cond-mat.stat-mech↗

arXiv2025

Flocking as a second-order phase transition in self-aligning active crystals

We study a two-dimensional crystal composed of active units governed by self-alignment. This mechanism induces a torque that aligns a particle's orientation with its velocity and leads to a phase transition from a disordered to a flocking crystal. Here, we provide the first microscopic theory that analytically maps the crystal dynamics onto a Landau-Ginzburg model, in which the velocity-dependent effective free energy undergoes a transition from a single-well shape to a Mexican-hat profile. As confirmed by simulations, our theory quantitatively predicts the transition point and characteristic spatial velocity correlations. The continuous change of the order parameter and the diverging behavior of the analytically predicted correlation length imply that flocking in self-aligning active crystals is a second-order phase transition. These findings provide a theoretical foundation for the flocking phenomenon observed experimentally in active granular particles and migrating cells.

cond-mat.soft↗

arXiv2025

Cluster sizes, particle displacements and currents in transport mediated by solitary cluster waves

In overdamped particle motion across periodic landscapes, solitary cluster waves can occur at high particle densities and lead to particle transport even in the absence of thermal noise. Here we show that for driven motion under a constant drag, the sum of all particle displacements per soliton equals one wavelength of the periodic potential. This unit displacement law is used to determine particle currents mediated by the solitons. We furthermore derive properties of clusters involved in the wave propagation as well as relations between cluster sizes and soliton numbers.

cond-mat.stat-mech↗

arXiv2025

Self-alignment and anti-self-alignment suppress motility-induced phase separation in active systems

In this article, we investigate the impact of self-alignment and anti-self-alignment on collective phenomena in dense active matter. These mechanisms correspond to effective torques that align or anti-align a particles orientation with its velocity, as observed in active granular systems. In the context of motility-induced phase separation (MIPS) - a non-equilibrium coexistence between a dense clustered phase and a dilute homogeneous phase - both self- and anti-self-alignment are found to suppress clustering. Specifically, increasing self-alignment strength first leads to flocking within the dense cluster, and eventually to the emergence of a homogeneous flocking phase. In contrast, anti-self-alignment induces a freezing phenomenon, progressively reducing particle speed until MIPS is suppressed and a homogeneous phase is recovered. These results are supported by scaling arguments and are amenable to experimental verification in high-density active granular systems exhibiting self- or anti-self-alignment.

cond-mat.soft↗

arXiv2025

Self-sustained frictional cooling in active matter

Cooling processes in nature are typically generated by external contact with a cold reservoir or bath. According to the laws of thermodynamics, the final temperature of a system is determined by the temperature of the environment. Here, we report a spontaneous internal cooling phenomenon for active particles, occurring without external contact. This effect, termed ``self-sustained frictional cooling'', arises from the interplay between activity and dry (Coulomb) friction, and in addition is self-sustained from particles densely caged by their neighbors. If an active particle moves in its cage, dry friction will stop any further motion after a collision with a neighbor particle thus cooling the particle down to an extremely low temperature. We demonstrate and verify this self-sustained cooling through experiments and simulations on active granular robots and identify dense frictional arrested clusters coexisting with hot, dilute regions. Our findings offer potential applications in two-dimensional swarm robotics, where activity and dry friction can serve as externally tunable mechanisms to regulate the swarm's dynamical and structural properties.

cond-mat.soft↗

arXiv2024

Solitary cluster waves in periodic potentials: Formation, propagation, and soliton-mediated particle transport

Transport processes in crowded periodic structures are often mediated by cooperative movements of particles forming clusters. Recent theoretical and experimental studies of driven Brownian motion of hard spheres showed that cluster-mediated transport in one-dimensional periodic potentials can proceed in form of solitary waves. We here give a comprehensive description of these solitons. Fundamental for our analysis is a static presoliton state, which is formed by a periodic arrangement of basic stable clusters. Their size follows from a geometric principle of minimum free space. Adding one particle to the presoliton state gives rise to solitons. We derive the minimal number of particles needed for soliton formation, number of solitons at larger particle numbers, soliton velocities and soliton-mediated particle currents. Incomplete relaxations of the basic clusters are responsible for an effective repulsive soliton-soliton interaction seen in measurements. A dynamical phase transition is predicted to occur in current-density relations at low temperatures. Our results provide a theoretical basis for describing experiments on cluster-mediated particle transport in periodic potentials.

cond-mat.stat-mech↗

arXiv2024

Inertial active matter with Coulomb friction

Friction is central to the motion of active (self-propelled) objects such as bacteria, animals, and robots. While in a viscous fluid friction is described by Stokes's law, objects in contact with other solid bodies are often governed by more complex empirical friction laws. Here, we study active particles subject to Coulomb friction using a combination of active granular experiments and simulations, supported by theoretical predictions. The interplay of friction and activity forces induces a rich behavior resulting in three distinct dynamical regimes. While for low activity, Brownian motion is recovered, for large activity we observe a dynamical Stop & Go regime that continuously switches from diffusion and accelerated motion. For greater activity, we observe a super-mobile dynamical regime characterized by a fully accelerated motion which is described by an anomalous scaling of the diffusion coefficient with the activity. These findings cannot be observed with Stokes viscous forces typical of active swimmers but are central in dry active objects.

cond-mat.soft↗

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↗

arXiv2024

Controlling Colloidal Flow through a Microfluidic Y-junction

Microscopic particles flowing through narrow channels may accumulate near bifurcation points provoking flow reduction, clogging and ultimately chip breakage. Here we show that the full flow behavior of colloidal particles through a microfluidic Y-junction (i.e. a three way intersection) can be controlled by tuning the pair interactions and the degree of confinement. By combining experiments with numerical simulations, we investigate the dynamic states emerging when magnetizable colloids flow through a symmetric Y-junction such that a single particle can pass through both gates with the same probability. We show that clogging can be avoided by repulsive interactions and branching into the two channels can be steered as well by interactions: attractive particles are flowing through the same gate, while repulsive colloids alternate between the two gates. Even details of the particle assembly such as buckling at the exit gate are tunable by interactions and the channel geometry.

cond-mat.soft↗

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↗