In this talk, I will present some of the ideas we have been studying in recent years concerning the effects of activity on the rheology of soft matter systems. First, I will explain how one can incorporate the effects of self-division and apoptosis into the usual elasto-plastic framework used for describing sheared dense soft matter systems [1,2]. Further, I will discuss how activity can give rise to a finite shear rate critical point, accompanied by giant fluctuations [3,4]. Lastly, I will explore how active terms in models used to study the yielding transition can help classify yielding as an absorbing phase transition belonging to a new universality class [5].

Through this talk, I aim to provide a comprehensive overview of our recent findings and the implications they have on our understanding of active matter rheology. I hope these insights can initiate interesting discussions regarding the link between traditional soft matter theory and the mechanical response of biological systems, such as confluent tissues.

[1] Matoz-Fernandez, Daniel A., et al. "Cell division and death inhibit glassy behavior of confluent tissues."

[2] Matoz-Fernandez, Daniel A., et al. "Nonlinear rheology in a model biological tissue." Physical Review Letters 118.15 (2017): 158105.

[3] Le Goff, Magali, et al. "Criticality at a finite strain rate in fluidized soft glassy materials." Physical Review Letters 123.10 (2019): 108003.

[4] Le Goff, Magali, et al. "Giant fluctuations in the flow of fluidized soft glassy materials: an elasto-plastic modeling approach." Journal of Physics: Materials 3.2 (2020): 025010.

[5] Jocteur, Tristan, et al. "Yielding is an absorbing phase transition with vanishing critical fluctuations." Physical Review Letters 132.26 (2024): 268203.