Renewing Active Matter: from competition to evolving materials

Proliferating active matter deals with non-equilibrium systems, driven microscopically by local growth, reproduction, and element removal. Natural multicellular systems such as tissues and biofilms are prime examples, with future applications also envisioned in synthetic cells. Dense systems of this sort can be described as soft matter, but can also exhibit novel features that are not available in inert and thermal matter or even in motility-driven active matter. For example, cell competition, which is the main focus of this talk, can lead to an evolution of the material composition and its properties. I will discuss stochastic competition for free space in confined systems with cell renewal and consider the special importance of passive matter elimination in this scenario, revealing a new fitness advantage. Such competition is of course relevant in a variety of biophysical processes including tissue morphogenesis and tumor growth, but here we will focus on its implications for the statistical physics of  renewing biomechanical materials that can change their mechanical properties.