arXiv subjects

Yutaka Kinoshita

Publications and source records attributed to Yutaka Kinoshita.

3 recordsLinked to original sources

arXiv2025

Active nematic liquid crystals under a quenched random field

Coupling between flow and orientation is a central issue in understanding the collective dynamics of active biofilaments and cells. Active stresses generated by motor activity destroy (quasi-)long-range orientational order and induce chaotic flows with many vortices. In cellular and subcellular environment, alignment is also hindered by heterogeneous filamentous structures in extracellular matrix and various intracellular organelles. Here we address the effects of a quenched random field on the flow patterns and orientational order in two-dimensional active nematic liquid crystals. We find that the director dynamics becomes frozen above a critical disorder strength. For sufficiently strong randomness, the orientational correlation function decays exponentially with distance, reproducing the behavior of passive random-field nematics. In contrast, the flow velocity decreases only gradually with increasing disorder, and exhibits a logarithmic spatial correlation under strong randomness. We identify the threshold between the activity- and disorder-dominated regimes and examine its dependence on the activity parameter.

cond-mat.soft↗

arXiv2024

Collective excitations in active solids featuring alignment interactions

With increasing emphasis on the study of active solids, the features of these classes of nonequilibrium systems and materials beyond their mere existence shift into focus. One concept of active solids addresses them as active, self-propelled units that are elastically linked to each other. The emergence of orientationally ordered, collectively moving states in such systems has been demonstrated. We here analyze the excitability of such collectively moving elastic states. To this end, we determine corresponding fluctuation spectra. They indicate that collectively excitable modes exist in the migrating solid. Differences arise when compared to those of corresponding passive solids. We provide evidence that the modes of excitation associated with the intrinsic fluctuations are related to corresponding modes of entropy production. Overall, we hope to stimulate by our investigation future experimental studies that focus on excitations in active solids.

cond-mat.soft↗

arXiv2023

Flow patterns and defect dynamics of active nematics under an electric field

The effects of an electric field on the flow patterns and defect dynamics of two-dimensional active nematics are numerically investigated. We found that field-induced director reorientation causes anisotropic active turbulence characterized by enhanced flow perpendicular to the electric field. The average flow speed and its anisotropy are maximized at an intermediate field strength. Topological defects in the anisotropic active turbulence are localized and show characteristic dynamics {with simultaneous creation of} two pairs of defects. A laning state characterized by stripe domains with alternating flow directions is found at a larger field strength near the transition to the uniformly aligned state. We obtained periodic oscillations between the laning state and active turbulence, which resembles an experimental observation of active nematics subject to anisotropic friction.

cond-mat.soft↗