Regensburg 2022 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 42: Statistical Physics of Biological Systems 2 (joint session BP/DY)

DY 42.5: Vortrag

Donnerstag, 8. September 2022, 16:00–16:15, H16

Order-disorder transition in epithelial tissues — •Kartik Chhajed, Marko Popović, and Frank Jülicher — Max Planck Institute for Physics of Complex Systems, Dresden

Two dimensional packings of cells in developing epithelial tissues are commonly found to be disordered. However, highly organised packings can emerge during development, such as hexagonal pattern of ommatidia in the eye epithelium of the fruit fly. Here, we observe a disorder to order transition in the packing of the fruit fly pupal wing epithelium. In particular, we find a sudden increase in the hexatic order parameter ψ₆, which suggests a presence of hexatic and crystalline phases in two dimensional systems, as described by the classical KTHNY theory. The melting transition scenario with the intermediate hexatic phase has been reproduced in a model of epithelial tissues [Pashupalak et al. Soft Matter, 2020] where the stochastic active forces generated by the cells play the role of an effective temperature. However, both KTHNY theory and recent literature on packings of epithelial tissues assume uniform properties of particles and cells, respectively. In a proliferating tissue cells grow and divide, which inevitably leads to a heterogeneity of cell sizes. Here, we use the vertex model of epithelial tissues to study how the disorder to order transition is affected by the heterogeneity of cell sizes. We find that reducing cell heterogeneity as a control parameter drives the system through an ordering transition. We compare our results with the experimental data of the fruit fly wing to identify the role of cell size heterogeneity in the observed disorder to order transition.