arXiv subjects

Dipanwita Ghoshal

Publications and source records attributed to Dipanwita Ghoshal.

3 recordsLinked to original sources

arXiv2026

Dynamical Facilitation in Active Glass Formers: Role of Morphology and Persistence

Understanding dynamical facilitation in nonequilibrium glass-forming systems driven by active forces remains an open challenge. In particular, it is unclear whether facilitation survives in active glasses, where persistent self-propulsion breaks detailed balance and introduces directional memory. Here, we use large-scale simulations of a two-dimensional athermal Ornstein-Uhlenbeck particle model to investigate how persistent active forcing modifies cooperative relaxation. We analyze the morphology of cooperatively rearranging regions (CRRs) and the spatial transport of mobility excitations. A spatially resolved core-shell decomposition reveals distinct responses of the core and shell to activity: the core undergoes global morphological changes while retaining internal plasticity, whereas the shell acts as a rigid scaffold that supports primarily axial deformation and facilitates transport. Dynamical observables, including modal displacement, shell occupation probability, and facilitation length, exhibit a pronounced non-monotonic dependence on persistence time. This behavior reflects the competition between persistence and effective noise, leading to either coherent or trapping-dominated dynamics at large persistence, depending on temperature. Despite significant morphological changes, the facilitation length shows an approximate scaling collapse when rescaled by the persistence length, $l_p=\sqrt{T_{\mathrm{eff}}τ_p}$. This is consistent with a diffusive-like time-length coupling, $ξ_{\mathrm{fac}} \sim τ_α^{1/2}$, indicating that activity reshapes facilitation pathways without altering their large-scale transport character. Our results support a generalized facilitation framework for active glass formers.

cond-mat.soft↗

arXiv2021

Morphology of cooperatively rearranging regions in active glass formers

Super cooled liquids display increasingly heterogeneous dynamics as temperature is lowered towards the glass transition ($T_{g}$). A hallmark of this dynamical heterogeneity is the spontaneous emergence of cooperative rearranging regions (CRRs) composed of fast moving particles. While these CRRs in passive glass formers have been explored in great detail, thus understanding is severely limited in active glass formers. The existing consensus on the morphology of CRRs in a passive glass former prioritizes its fast subsets, composed of fast moving particles. In the present study, we focus on a synthetic athermal active glass former and show an equal contribution for the morphology of CRRs from slow subsets as well. Both these subsets exhibit an exponential distribution in their structure which strongly correlates with the existence of CRRs. Interestingly, we also observe that the fractal dimensions ($d_{\text{f}}$) of these subsets share both string and compact like morphology that tends to vary in opposite fashion with the control parameters, namely the persistent time ($τ_{p}$) and the effective temperature ($T_{\text{eff}}$). The fractal dimension $d_{\text{f}}$ measures the roughness or put simply the compactness of fractal objects at their boundaries. More precisely, molecules are loosely bound in a structure for which boundary is rough and thereby this condition facilitates its structural change in terms of size and shape. It is also a fact that any structural change is a signature of relaxation dynamics in the context of glass forming liquids. Thus, in the present study, we observe a change in $d_{\text{f}}$ with $T_{\text{eff}}$ and $τ_{p}$ from the insights of morphology variation that causes structural change, both in the BD limit and non-equilibrium limit.

cond-mat.soft↗

arXiv2020

Connecting Relaxation Time to a Dynamical Length Scale in Athermal Active Glass Formers

Supercooled liquids display dynamics that are inherently heterogeneous in space. This essentially means that at temperatures below the melting point, particle dynamics in certain regions of the liquid can be orders of magnitude faster than other regions. Often dubbed as dynamical heterogeneity, this behavior has fascinated researchers involved in the study of glass transition, for over two decades. A fundamentally important question in all glass transition studies is whether one can connect the growing relaxation time to a concomitantly growing length scale. In this paper, we go beyond the realm of ordinary glass forming liquids and study the origin of a growing dynamical length scale $ξ$ in a self propelled "active" glass former. This length scale which is constructed using structural correlations agrees well with the average size of the clusters of slow moving particles that are formed as the liquid becomes spatially heterogeneous. We further report that the concomitantly growing $α$- relaxation time exhibits a simple scaling law, $τ_α\sim \text{exp} (ξμ/ T_{eff})$, with $μ$ as an effective chemical potential, $T_{eff}$ as the effective temperature, and $ξμ$ as the growing free energy barrier for cluster rearrangements. The findings of our study are valid over three decades of persistence times, and hence could be very useful in understanding the slow dynamics of a generic active liquid such as an active colloidal suspension, or a self propelled granular medium, to mention a few.

cond-mat.soft↗