arXiv subjects

Pushpita Ghosh

Publications and source records attributed to Pushpita Ghosh.

5 recordsLinked to original sources

arXiv2026

Thermal feedback as a kinetic control mechanism in reaction-diffusion pattern formation

Pattern formation in reaction-diffusion systems is traditionally analyzed under isothermal assumptions, overlooking the dynamical role of temperature in systems where reactions generate and dissipate heat. Here, we investigate non-isothermal reaction-diffusion dynamics by coupling activator-inhibitor kinetics to a dynamically evolving temperature field that modulates reaction rates through Arrhenius-type dependencies. This coupling introduces an additional feedback mechanism that influences stability and pattern selection. Through analytical and numerical analysis of the Cholrine dioxide-Iodine-Malonic acid (CDIMA) and Schnakenberg models, we demonstrate that thermal feedback modifies dispersion relations by enhancing instability growth rates and shifting pattern selection toward shorter wavelengths. Beyond these intrinsic effects, we identify a boundary-mediated mechanism in which thermal constraints qualitatively alter global dynamics. In particular, fixed-temperature boundaries induce nonstationary behavior in the CDIMA system, whereas the Schnakenberg model exhibits robust stationary patterns. These results establish thermal-kinetic coupling as a general mechanism for controlling pattern formation and highlight the role of boundary-mediated heat exchange as a tunable parameter for spatiotemporal organization.

physics.chem-ph↗

arXiv2026

Reaction-transport coupling drives spatiotemporal organization in fuel-driven supramolecular polymerization

Chemically fueled supramolecular systems provide a versatile platform for generating nonequilibrium structures and dynamical instabilities, including chemical oscillations and traveling waves reminiscent of biological organization. However, a minimal mechanistic framework capable of capturing the emergence of such spatiotemporal order is still lacking. Here, we develop a minimal reaction-transport framework for fuel-driven supramolecular polymerization that couples activation-deactivation chemistry with cooperative assembly, fragmentation, and polymer length-dependent diffusion. The model captures autonomous oscillations arising through a Hopf bifurcation and demonstrates how temporal instabilities evolve into spatial self-organization upon inclusion of transport. We show that the nonlinear interplay between reaction kinetics and state-dependent mobility gives rise to traveling polymerization fronts, oscillatory wave dynamics, and complex spatiotemporal patterns. The propagating fronts exhibit near-ballistic dynamics, revealing a fundamentally nonequilibrium transport mechanism emerging from reactive feedback and dynamically evolving diffusivity. These findings establish a minimal physical framework connecting dissipative self-assembly, nonlinear transport, and active matter, while providing design principles for programmable supramolecular materials capable of autonomous spatiotemporal organization.

cond-mat.soft↗

arXiv2020

Nonlinear dynamics of emergent traveling waves in a reaction-Cattaneo system

Standard diffusion equation is based on Brownian motion of the dispersing species without considering persistence in the movement of the individuals. This description allows for the instantaneous spreading of the transported species over an arbitrarily large distances from their original location predicting infinite velocities. This feature is unrealistic particularly while considering biological invasion dynamics and a better description needs the consideration of dispersal with inertia. We here examine the behavior of non-infinitesimal perturbation on the steady state of an one-dimensional reaction-Cattaneo system with a cubic polynomial source term describing population dynamics or flame propagation models. It has been shown analytically that while linear analysis predicts stability of the homogeneous state, consideration of nonlinear contribution leads to a growth of spatiotemporal perturbation as a traveling wave. We show that the presence of a small finite relaxation time of the diffusive flux modifies the speed of the traveling wave. Specifically, we find that the wave speed decays with an increase of a finite relaxation time of flux. Our analytical predictions are well corroborated with the numerical results.

nlin.PS↗

arXiv2018

Mechanisms for bacterial gliding motility on soft substrates

The motility mechanism of certain rod-shaped bacteria has long been a mystery, since no external appendages are involved in their motion which is known as gliding. However, the physical principles behind gliding motility still remain poorly understood. Using myxobacteria as a canonical example of such organisms, we identify here the physical principles behind gliding motility, and develop a theoretical model that predicts a two-regime behavior of the gliding speed as a function of the substrate stiffness. Our theory describes the elastic, viscous, and capillary interactions between the bacterial membrane carrying a traveling wave, the secreted slime acting as a lubricating film, and the substrate which we model as a soft solid. Defining the myxobacterial gliding as the horizontal motion on the substrate under zero net force, we find the two-regime behavior is due to two different mechanisms of motility thrust. On stiff substrates, the thrust arises from the bacterial shape deformations creating a flow of slime that exerts a pressure along the bacterial length. This pressure in conjunction with the bacterial shape provides the necessary thrust for propulsion. However, we show that such a mechanism cannot lead to gliding on very soft substrates. Instead, we show that capillary effects lead to the formation of a ridge at the slime-substrate-air interface, which creates a thrust in the form of a localized pressure gradient at the tip of the bacteria. To test our theory, we perform experiments with isolated cells on agar substrates of varying stiffness and find the measured gliding speeds to be in good agreement with the predictions from our elasto-capillary-hydrodynamic model. The physical mechanisms reported here serve as an important step towards an accurate theory of friction and substrate-mediated interaction between bacteria in a swarm of cells proliferating in soft media.

physics.bio-ph↗

arXiv2017

Spreading of non-motile bacteria on a hard agar plate: Comparison between agent-based and stochastic simulations

We study spreading of a non-motile bacteria colony on a hard agar plate by using agent-based and continuum models. We show that the spreading dynamics depends on the initial nutrient concentration, the motility and the inherent demographic noise. Population fluctuations are inherent in an agent based model whereas, for the continuum model we model them by using a stochastic Langevin equation. We show that the intrinsic population fluctuations coupled with non-linear diffusivity lead to a transition from Diffusion Limited Aggregation (DLA) type morphology to an Eden-like morphology on decreasing the initial nutrient concentration.

physics.comp-ph↗