| 03/2023 Hydrodynamics of an odd active surfer in a chiral fluid Yuto Hosaka et al. We theoretically and computationally study the low-Reynolds-number hydrodynamics of a linear active microswimmer surfing on a compressible thin fluid layer characterized by an odd viscosity. In the limit of small odd viscosity compared to the even viscosities of the fluid layer, we obtain analytical expressions for the self-induced flow field, which includes non-reciprocal components due to the od … |
| 03/2023 Self-organization of primitive metabolic cycles due to non-reciprocal interactions Vincent Ouazan-Reboul et al. We study analytically and numerically a model metabolic cycle composed of an arbitrary number of species of catalytically active particles. Each species converts a substrate into a product, the latter being used as the substrate by the next species in the cycle. Through a combination of catalytic activity and chemotactic mobility, the active particles develop effective non-reciprocal interactions … |
| 03/2023 Collective synchronization of dissipatively-coupled noise-activated processes Michalis Chatzittofi et al. A system of two enzymes mechanically coupled to each other in a viscous medium was recently studied, and conditions for obtaining synchronization and an enhanced average rate of the thermally-activated catalytic reactions of the enzymes were identified. The transition to synchronization occurred as the result of a global bifurcation in the underlying dynamical system. Here, we extend and generaliz … |
| 03/2023 Reentrant condensation transition in a model of driven scalar active matter with diffusivity edge Jonas Berx et al. The effect of a diffusivity edge is studied in a system of scalar active matter confined by a periodic potential and driven by an externally applied force. We find that this system shows qualitatively distinct stationary regimes depending on the amplitude of the driving force with respect to the potential barrier. For small driving, the diffusivity edge induces a transition to a condensed phase an … |
| 02/2023 Accurate dynamics from self-consistent memory in stochastic chemical reactions with small copy numbers Moshir Harsh et al. We present a method that captures the fluctuations beyond mean field in chemical reactions in the regime of small copy numbers and hence large fluctuations, using self-consistently determined memory: by integrating information from the past we can systematically improve our approximation for the dynamics of chemical reactions. This memory emerges from a perturbative treatment of the effective acti … |
| 02/2023 Hydrodynamic instabilities in a 2-D sheet of microswimmers embedded in a 3-D fluid Viktor Škultéty et al. A collection of microswimmers immersed in an incompressible fluid is characterised by strong interactions due to the long-range nature of the hydrodynamic fields generated by individual organisms. As a result, suspensions of rear-actuated `pusher' swimmers such as bacteria exhibit a collective motion state often referred to as `bacterial turbulence', characterised by large-scale chaotic … |
| 02/2023 Interplay between Brownian and hydrodynamic tracer diffusion in suspensions of swimming microorganisms Henrik Nordanger et al. The general problem of tracer diffusion in non-equilibrium baths is important in a wide range of systems, from the cellular level to geographical lengthscales. In this paper, we revisit the archetypical example of such a system: a collection of small passive particles immersed in a dilute suspension of non-interacting dipolar microswimmers, representing bacteria or algae. In particular, we conside … |
| 02/2023 Long-range Velocity Correlations from Active Dopants Leila Abbaspour et al. One of the most remarkable observations in dense active matter systems is the appearance of long-range velocity correlations without any explicit aligning interaction (of e.g.\ Vicsek type). Here we show that this kind of long range velocity correlation can also be generated in a dense athermal passive system by the inclusion of a very small fraction of active Brownian particles. We develop a cont … |
| 02/2023 Physical interactions promote Turing patterns Lucas Menou et al. Turing's mechanism is often invoked to explain periodic patterns in nature, although direct experimental support is scarce. Turing patterns form in reaction-diffusion systems when the activating species diffuses much slower than the inhibiting species, and the involved reactions are highly non-linear. Such reactions can originate from co-operativity, whose physical interactions should also af … |
| 02/2023 Minimum Entropy Production by Microswimmers with Internal Dissipation Abdallah Daddi-Moussa-Ider et al. The energy dissipation and entropy production by self-propelled microswimmers differ profoundly from passive particles pulled by external forces. The difference extends both to the shape of the flow around the swimmer, as well as to the internal dissipation of the propulsion mechanism. Here we derive a general theorem that provides an exact lower bound on the total, external and internal, dissipat … |