arXiv subjects

Nayana Venkatareddy

Publications and source records attributed to Nayana Venkatareddy.

6 recordsLinked to original sources

arXiv2026

Two-Temperature Induced Phase Separation: Non-equilibrium Phase Behavior, Ordering, and Kinetics

Two-temperature induced phase separation (2-TIPS) has emerged as a generic non-equilibrium mechanism in scalar active systems with heterogeneous activity, where particles coupled to different thermal reservoirs spontaneously demix into dense cold and dilute hot phases. Unlike equilibrium phase separation or motility-induced phase separation (MIPS), 2-TIPS is driven solely by unequal energy injection and the resulting heat flux between particle species. This review summarizes recent advances in 2-TIPS across diverse soft-matter systems, highlighting both its universal non-equilibrium mechanisms and the emergent ordered phases arising from particle shape anisotropy, chirality, confinement, and topology. We further discuss density-dependent phase-separation kinetics and coarse-grained descriptions linking microscopic dynamics to macroscopic behavior, and outline key directions for future research.

cond-mat.soft↗

arXiv2026

Density-Induced Reentrant Coarsening in a Two-Temperature System

Understanding how nonequilibrium driving modifies phase-separation kinetics remains a fundamental challenge. Here we show that phase separation in a two-temperature system exhibits a striking density-induced reentrant coarsening behavior. Using Brownian dynamics simulations and a coarse-grained field-theoretic model, we find that the characteristic domain size grows as $L(t)\sim t^{1/z}$, displaying a reentrant sequence $(t^{1/3} \rightarrow t^{1/4}\rightarrow t^{1/3})$ with increasing density. While the low- and high-density regimes are governed by classical curvature-driven bulk diffusion, the intermediate-density regime exhibits anomalously slow growth. We show that this slowdown originates from a transport bottleneck arising from the interplay of particle diffusivity, particle availability, and attachment kinetics, which suppresses the effective mass flux between domains. Unlike equilibrium phase separation, where density primarily affects morphology and crossover scales, the two-temperature drive renders density a key control parameter for coarsening pathways. Our results uncover a nonequilibrium mechanism for anomalous domain growth in two-temperature systems.

cond-mat.soft↗

arXiv2025

Phase separation kinetics of 2-TIPS at low density: Cluster growth by ballistic agglomeration

We study the kinetics of two-temperature induced phase separation (2-TIPS) in dilute binary mixtures of active ("hot") and passive ("cold") particles using molecular dynamics simulations and a coarse-grained hydrodynamic model. Following a temperature quench, cold particles nucleate into mobile clusters that move ballistically and merge through successive coalescence events. The resulting domain growth exhibits dynamic scaling with a growth exponent of approximately 0.7, markedly faster than diffusive coarsening. We identify this regime as ballistic agglomeration of cold clusters, demonstrating a distinct nonequilibrium growth mechanism in low-density scalar active systems.

cond-mat.soft↗

arXiv2025

Diffusion-entropy scaling across dimensions

A quantitative relationship between the diffusion coefficient $D$ of a tagged particle in a liquid and the entropy $S$ of that liquid has long been sought, as it would allow entropy to be inferred directly from diffusion measurements and transport properties to be predicted from thermodynamic information. Here, we employ extensive computer simulations to independently compute both $D$ and $S$ for Lennard-Jones (LJ) liquids and for water across a wide range of thermodynamic state points. Our study covers two and three dimensions for both systems, and additionally explores one-dimensional confinement for water. We find that the ratio of diffusion coefficients between two states follows an almost perfect exponential dependence on their entropy difference. For LJ liquids, the exponential prefactor exhibits a pronounced dependence on dimensionality $d$, consistent in trend but quantitatively distinct from theoretical predictions. In contrast, water shows a strikingly weak dimensionality $d$ dependence, deviating from theory, which we attribute to the dominant role of jump diffusion. Remarkably, the exponential diffusion-entropy relationship persists even when translational and rotational contributions to entropy are separated and considered individually. This robustness suggests that entropy provides a unifying measure governing particle mobility in liquids, largely independent of microscopic mechanisms or dimensional constraints.

cond-mat.stat-mech↗

arXiv2025

Growth Laws and Universality in 2-TIPS: Microscopic and Coarse grained approach

Two temperature induced phase separation(2-TIPS) is a phenomenon observed in mixtures of active and passive particles modeled by scalar activity where the temperature of the particle is proportional to its activity. The binary mixture of 'hot' and 'cold' particles phase separate when the relative temperature difference between hot and cold particles defined as activity $χ$ exceeds a density dependent critical value. The study of kinetics in 2-TIPS, a non-equilibrium phase separation, is of fundamental importance in statistical physics. In this paper, we investigate 2-TIPS kinetics using molecular dynamics (MD) and coarse-grained (CG) modeling in 3D and 2D. The coarse-grained model couples two passive Model B equations for hot and cold particles, with coupling terms emulating the energy transfer between them by raising the temperature of cold particles and lowering that of hot particles, a key observation from the MD simulations. MD simulations reveal that at high densities, phase separation begins immediately after the quench, forming bi-continuous domains rich in hot or cold particles, similar to spinodal decomposition in passive systems. These interconnected domains are also observed in the coarse-grained model for the mixture's critical composition. Both MD and CG models show dynamic scaling of the correlation function, indicating self-similar domain growth. Regardless of dimensionality, both methods report algebraic growth in domain length with a growth exponent of $1/3$, known as the Lifshitz-Slyozov exponent, widely observed in passive systems. Our results demonstrate that the universality of phase separation kinetics observed in passive systems also extends to the non-equilibrium binary mixture undergoing 2-TIPS.

cond-mat.soft↗

arXiv2023

Effect of Confinement and Topology: 2-TIPS vs MIPS

2-TIPS (Two Temperature induced phase separation) refers to the phase separation phenomenon observed in mixtures of active and passive particles which are modelled using scalar activity. The active particles are connected to a thermostat at high temperature while the passive particles are connected to the thermostat at low temperature and the relative temperature difference between "hot" and "cold" particles is taken as the measure of the activity of the non-equilibrium system. The study of such binary mixtures of hot and cold particles under various kinds of confinement is an important problem in many physical and biological processes. The nature and extent of phase separation are heavily influenced by the geometry of confinement, activity, and density of the non-equilibrium binary mixture. Investigating such 3D binary mixtures confined by parallel walls, we observe that, the active and passive particles phase separate, but the extent of phase separation is reduced compared to bulk phase separation at high densities and enhanced at low densities. However, when the binary mixture of active and passive particles is confined inside a spherical cavity, the phase separation is radial for small radii of the confining sphere and the extent of phase separation is higher compared to their bulk counterparts. Confinement leads to interesting properties in the passive(cold) region like enhanced layering and high compression in the direction parallel to the confining wall. In 2D, both the bulk and confined systems of the binary mixture show a significant decrement in the extent of phase separation at higher densities. This observation is attributed to the trapping of active particles inside the passive cluster, which increases with density. similar phase co-existence.

cond-mat.soft↗