Driving potential and noise level determine the synchronization state of hydrodynamically coupled oscillators

Synchronization has been such a central topic in science over the last 50 years that one wonders whether new breakthroughs are possible. Contrary to this expectation, recent work on cilia and flagella hydrodynamics paints a new ``shade'' of synchronization, with experimental and theoretical evidence supporting the original hypothesis by Taylor in the 50s, that coordinated beating is caused by the interactions through the surrounding fluid.

Understanding this physical problem has large biological importance, since cilia and flagella are ubiquitous in eukaryotes, key to the functionality of diverse human tissues, and possibly played a role in the evolution of multicellularity.

Central questions are how the internal engine of cilia integrates the cues coming from the fluid in order to achieve (and lose) synchronization with neighbours, and how dynamic states of many oscillators are maintained.

Current technology allows to build micron-scale active units that exhibit hydrodynamic synchronization, and are simple to describe theoretically, allowing quantitative studies. This talk will present a configuration-dependent geometric-switch feedback system, driving colloidal particles with optical traps.

We show how the internal force engine with which the active unit pushes the fluid during each beating cycle, i.e. the driving potential, determines the dynamical steady state in competition with thermal noise. In many-oscillator systems, we show how the dynamical state can be predicted on the basis of the equilibrium coupling tensor.