Viktor Holubec
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View article: Order-Disorder Transition and Phase Separation in Delay Vicsek Model
Order-Disorder Transition and Phase Separation in Delay Vicsek Model Open
Interactions in active matter systems inherently involve delays due to information processing and actuation lags. We numerically investigate the impact of such delays on the phase behavior of the Vicsek model for motile active matter at a …
View article: Optimizing low-dissipation Carnot-like thermal devices with heat leak
Optimizing low-dissipation Carnot-like thermal devices with heat leak Open
Delimiting the optimal performance bounds of heat engines (HEs), refrigerators (REs), and heat pumps (HPs) is a core thermodynamic challenge. While low-dissipation (LD) models are valuable for this, the impact of heat leak-unavoidable in r…
View article: Inertia Tames Fluctuations in Autonomous Stationary Heat Engines
Inertia Tames Fluctuations in Autonomous Stationary Heat Engines Open
Thermodynamic uncertainty relations (TURs) provide fundamental constraints on the interplay between power fluctuations, entropy production, and efficiency in overdamped stationary autonomous heat engines. However, their validity in underda…
View article: Active Matter Flocking via Predictive Alignment
Active Matter Flocking via Predictive Alignment Open
Understanding collective self-organization in active matter, such as bird flocks and fish schools, remains a grand challenge in physics. Interactions that induce alignment are essential for flocking; however, alignment alone is generally i…
View article: Optimal constrained control for generally damped Brownian heat engines
Optimal constrained control for generally damped Brownian heat engines Open
Optimization of cyclic stochastic heat engines, a topic spanning decades of research, commonly assumes fixed control or response parameters at discrete points in the cycle-a limitation that often leads to experimentally impractical protoco…
View article: Active Matter Flocking via Predictive Alignment
Active Matter Flocking via Predictive Alignment Open
Understanding collective self-organization in active matter, such as bird flocks and fish schools, remains a grand challenge in physics. Alignment interactions are essential for flocking, yet alone, they are generally considered insufficie…
View article: Run-and-tumble motion of ellipsoidal microswimmers
Run-and-tumble motion of ellipsoidal microswimmers Open
A hallmark of bacteria is their so-called “run-and-tumble” motion and its variants, consisting of a sequence of linear directed “runs” and distinct rotation events that constantly alternate due to biochemical feedback. It plays a crucial r…
View article: Corrigendum: Matrix numerical method for probability densities of stochastic delay differential equations (2024 J. Phys. A: Math. Theor. 57 235001)
Corrigendum: Matrix numerical method for probability densities of stochastic delay differential equations (2024 J. Phys. A: Math. Theor. 57 235001) Open
We correct typos in equations (8), (9), and (12) of the original paper.
View article: Matrix numerical method for probability densities of stochastic delay differential equations
Matrix numerical method for probability densities of stochastic delay differential equations Open
Stochastic processes with time delay are invaluable for modeling in science and engineering when finite signal transmission and processing speeds can not be neglected. However, they can seldom be treated with sufficient precision analytica…
View article: Run-and-tumble motion of ellipsoidal microswimmers
Run-and-tumble motion of ellipsoidal microswimmers Open
A hallmark of bacteria is their so-called "run-and-tumble" motion, consisting of a sequence of linear directed "runs" and random rotations that constantly alternate due to biochemical feedback. It plays a crucial role in the ability of bac…
View article: Active particles with delayed attractions form quaking crystallites <sup>(a)</sup>
Active particles with delayed attractions form quaking crystallites <sup>(a)</sup> Open
Perception-reaction delays have experimentally been found to cause a spontaneous circling of microswimmers around a fixed target particle. Here we investigate a many-body version of such an experiment with Brownian-dynamics simulations of …
View article: Force-free and autonomous active Brownian ratchets <sup>(a)</sup>
Force-free and autonomous active Brownian ratchets <sup>(a)</sup> Open
Autonomous active Brownian ratchets rectify active Brownian particle motion solely by means of a spatially modulated but stationary activity, without external forces. We argue that such ratcheting requires at least a two-dimensional geomet…
View article: Force-Free and Autonomous Active Brownian Ratchets
Force-Free and Autonomous Active Brownian Ratchets Open
Autonomous active Brownian ratchets rectify active Brownian particle motion solely by means of a spatially modulated but stationary activity, without external forces. We argue that such ratcheting requires at least a two-dimensional geomet…
View article: Active particles with delayed attractions form quaking crystallites
Active particles with delayed attractions form quaking crystallites Open
Perception-reaction delays have experimentally been found to cause a spontaneous circling of microswimmers around a targeted center. Here we investigate the many-body version of this experiment with Brownian-dynamics simulations of active …
View article: Spontaneous vortex formation by microswimmers with retarded attractions
Spontaneous vortex formation by microswimmers with retarded attractions Open
Collective states of inanimate particles self-assemble through physical interactions and thermal motion. Despite some phenomenological resemblance, including signatures of criticality, the autonomous dynamics that binds motile agents into …
View article: Optimal finite-time heat engines under constrained control
Optimal finite-time heat engines under constrained control Open
We optimize finite-time stochastic heat engines with a periodically scaled\nHamiltonian under experimentally motivated constraints on the bath temperature\n$T$ and the scaling parameter $\\lambda$. We present a general geometric proof\ntha…
View article: Signal propagation and linear response in the delay Vicsek model
Signal propagation and linear response in the delay Vicsek model Open
Retardation between sensation and action is an inherent biological trait. Here we study its effect in the Vicsek model, which is a paradigmatic swarm model. We find that (1) a discrete time delay in the orientational interactions diminishe…
View article: Information conduction and convection in noiseless Vicsek flocks
Information conduction and convection in noiseless Vicsek flocks Open
Physical interactions generally respect certain symmetries, such as reciprocity and energy conservation, which survive in coarse grained isothermal descriptions. Active many-body systems usually break such symmetries intrinsically, on the …
View article: Signal propagation and linear response in the delay Vicsek model
Signal propagation and linear response in the delay Vicsek model Open
Retardation between sensation and action is an inherent biological trait. Here we study its effect in the Vicsek model, which is a paradigmatic swarm model. We find that: (i) a discrete time delay in the orientational interactions diminish…
View article: Thermodynamics and optimal protocols of multidimensional quadratic Brownian systems
Thermodynamics and optimal protocols of multidimensional quadratic Brownian systems Open
We characterize finite-time thermodynamic processes of multidimensional quadratic overdamped systems. Analytic expressions are provided for heat, work, and dissipation for any evolution of the system covariance matrix. The Bures-Wasserstei…
View article: Thermodynamics and optimal protocols of multidimensional quadratic Brownian systems
Thermodynamics and optimal protocols of multidimensional quadratic Brownian systems Open
We characterize finite-time thermodynamic processes of multidimensional quadratic overdamped systems. Analytic expressions are provided for heat, work, and dissipation for any evolution of the system covariance matrix. The Bures-Wasserstei…
View article: Equilibrium stochastic delay processes
Equilibrium stochastic delay processes Open
Stochastic processes with temporal delay play an important role in science and engineering whenever finite speeds of signal transmission and processing occur. However, an exact mathematical analysis of their dynamics and thermodynamics is …
View article: Fluctuations in heat engines
Fluctuations in heat engines Open
At the dawn of thermodynamics, Carnot’s constraint on efficiency of heat engines stimulated the formulation of one of the most universal physical principles, the second law of thermodynamics. In recent years, the field of heat engines acqu…
View article: Density and polarization of active Brownian particles in curved activity landscapes
Density and polarization of active Brownian particles in curved activity landscapes Open
Suspensions of motile active particles with space-dependent activity form characteristic polarization and density patterns. Recent single-particle studies for planar activity landscapes identified several quantities associated with emergen…
View article: Polarization-density patterns of active particles in motility gradients
Polarization-density patterns of active particles in motility gradients Open
The colocalization of density modulations and particle polarization is a characteristic emergent feature of motile active matter in activity gradients. We employ the active-Brownian-particle model to derive precise analytical expressions f…
View article: How Activity Landscapes Polarize Microswimmers without Alignment Forces
How Activity Landscapes Polarize Microswimmers without Alignment Forces Open
Active-particle suspensions exhibit distinct polarization-density patterns in activity landscapes, even without anisotropic particle interactions. Such polarization without alignment forces is at work in motility-induced phase separation a…
View article: Maximum efficiency of absorption refrigerators at arbitrary cooling power
Maximum efficiency of absorption refrigerators at arbitrary cooling power Open
We consider absorption refrigerators consisting of simultaneously operating Carnot-type heat engine and refrigerator. Their maximum efficiency at given power (MEGP) is given by the product of MEGPs for the internal engine and refrigerator.…
View article: Underdamped active Brownian heat engine
Underdamped active Brownian heat engine Open
Active Brownian engines rectify energy from reservoirs composed of self-propelling nonequilibrium molecules into work. We consider a class of such engines based on an underdamped Brownian particle trapped in a power-law potential. The ener…
View article: Active Brownian heat engines
Active Brownian heat engines Open
When do nonequilibrium forms of disordered energy qualify as heat? We address this question in the context of cyclically operating heat engines feeding on nonequilibrium energy reservoirs that defy the zeroth law of thermodynamics into wor…