From swarms of swimming bacteria to the moving contents of cells, biology is replete with active systems whose microscopic constituents interact by performing mechanical work on a surrounding fluidic medium. This can lead to large-scale, sometimes functional, self-organized structures and complex dynamics. I'll overview the modeling of such systems, focusing first on continuum kinetic theories that couple the micro and macroscopic scales to describe how suspensions of active particles, such as swimming microorganisms, evolve in time. While high-dimensional (5+1) these models have been used to understand observations of novel instabilities, turbulent-like dynamics, and strange rheology, and have been incorporated into more complex models of biological systems. I'll then pivot to describe the emergence of large scale, spontaneously appearing transport flows in developing egg cells. Building on a conception of molecular motors carrying payloads on a flexible polymer assembly, I'll develop an active porous medium model whose instabilities naturally drive the system towards large-scale "twister" flows consistent with experiments.

Superconducting resonators are technological building blocks for experiments in quantum computing, cosmology, and particle physics. Yet, despite their prevalence, in some limits they can exhibit rich and poorly understood behavior. Resonators formed from an array of Josephson junctions are a prime example. I will present two studies exploring their physics. The first study shows that apparent superconductivity persists for vastly weaker arrays than expected within a zero-temperature theory. This behavior is consistent with thermal effects, which effectively melt the insulator and restore superconducting behavior [1]. The second study explores a source of dissipation arising from photon-photon interactions — photonic “friction”. I will discuss our current efforts to characterize both decay rates and kinetics associated with this effect.

[1] S. Mukhopadhyay et al., Nat. Phys. 19 (2023) 1630.