ETD

• active matter
• out of equilibrium
• soft matter

When the heartbeat becomes irregular due to tachycardia or fibrillation, on the sur- face of the heart spiral waves and turbulence emerge. Recently, a many-body model for catching the spontaneous emergence of waves in contractile biological tissues has been proposed: tissues are therein treated as a dense assembly of active deforming particles. In this model, a dense system of active particles is considered. Each particle has a circular shape and can change its radius following an internal drive and pairwise interactions.
However, cells such as cardiomyocytes (heart cells able to contract rhythmically) are not isotropic. Therefore we add a new degree of freedom represented by the ability of particles to change their eccentricity depending on their phase. Thus we investigate the role of anisotropy in collective dynamics using four different models of deformable pul- sating ellipses. The resulting dynamics are studied through numerical simulations and hydrodynamic equations, obtained from coarse-graining of the microscopic dynamics. This model paves the way for simulating contractile biological tissues, elucidates the interplay between nematic order and size synchronization, and gives some insights into how cell deformability might control the emergence of spiral waves and wave turbulence in cardiac tissues.