arXiv subjects

Abhra Puitandy

Publications and source records attributed to Abhra Puitandy.

4 recordsLinked to original sources

arXiv2026

Emergent Rotation of Passive Clusters in a Chiral Active Bath

We investigate the dynamics of passive particles immersed in a bath of chiral active particles, focusing on the emergence of collective rotational motion. Using numerical simulations, we show that passive particles aggregate into clusters that can exhibit persistent rotation within a well-defined regime of size ratio and active particle packing fraction. This rotational state is characterized by the coexistence of internal structural order, enhanced shape fluctuations, and a coherent net torque generated by the surrounding active bath. Outside this regime, the dynamics remain predominantly diffusive, highlighting that sustained rotation is not ubiquitous but arises from a delicate interplay between geometry, activity, and chirality. Furthermore, we demonstrate that chirality heterogeneity disrupts rotational coherence, while a uniform chiral bath promotes strongly superdiffusive angular dynamics. These results provide new insights into the role of chirality and collective interactions in shaping the emergent behavior of active-passive mixtures.

cond-mat.soft↗

arXiv2025

Analytical Theory of Chiral Active Particle Transport in a Fluctuating Density Field

We develop a closed-form analytical theory for the transport of a chiral active Brownian particle in three dimensions, moving through a fluctuating local density field that models steric and dynamical interactions in a dense active medium. The density field is modeled as an Ornstein--Uhlenbeck process with finite correlation time $\tau$ and fluctuation strength $\sigma_\rho^2$, capturing both spatial fluctuations and temporal memory. Within this framework, we derive exact expressions for the mean-squared displacement and time-dependent diffusivity, revealing how chirality and density coupling jointly renormalise orientational persistence and generate nontrivial dynamical crossovers. The theory predicts: (i) anomalously high initial diffusivity for particles starting in locally denser regions, arising from a transient active drift driven by local swim-pressure gradients; (ii) a finite crossover time $t_c$ for homogenising density inhomogeneities, with a transient dependence of the dynamics on the initial local density environment which arises from the non-equilibrium evolution of density fluctuations and does not persist when averaging over stationary initial conditions ($\rho_0 = \rho_\infty$) ; (iii) a non-monotonic $t_c(\Omega)$ with a global minimum at intermediate chirality, and a three-regime suppression of long-time diffusivity $D_\infty(\Omega)$, consistent with micro-clustered phases observed in simulations; and (iv) a resonance-like peak in the early-time oscillatory strength of the mean-squared displacement at an optimal chirality $\Omega^*$, set by the interplay of orientational diffusion, density-field decorrelation, and imposed rotation. The framework captures the qualitative dependence of $D_\infty$ on $Pe$ and $\Omega$, {where Pe denotes the P\'eclet number}, while uncovering chirality-dependent transport features in active matter.

cond-mat.stat-mech↗

arXiv2025

Spontaneous Rotation of a Symmetric Inclusion in Chiral Active Bath

We study the dynamics of a circular passive inclusion, termed a torquer, in a bath of chiral active Brownian particles. Despite being geometrically symmetric and non-motile, the torquer exhibits persistent rotation due to spatially inhomogeneous torques arising from angularly biased collisions with active particles. This interaction-driven symmetry breaking does not rely on shape anisotropy or external forcing. Through simulations, we identify two distinct regimes of rotation: one dominated by density gradients at low chirality, and another by increased impact frequency at high chirality. Our results highlight how nonequilibrium interactions in chiral active media can induce motion in symmetric objects, offering a new perspective on symmetry breaking in active systems.

cond-mat.soft↗

arXiv2024

Directional cues affect the collective behaviour of Self propelled particles in one dimension

This study explores the effect of quenched disorder on the characteristic of self-propelled particles in one-dimension. Here,particles interact with disorder which serve as directional cues. The study investigates how the density of the disorder influence the emergence of ordering and clustering in the collection of the self propelled particles. We introduce the microscopic model as well as corresponding coarse-grained equations of motion for the local density and the orientation of particle. Disorder affects the macroscopic ordering in the system, the size of the ordered clusters decays algebraically with disorder. Further, the disorder also affects the clustering of particles; in the presence of disorder, a big macroscopic cluster breaks into small clusters, leads to the localization of particles around it and results in high density around the disorder.

cond-mat.soft↗