Non-Gaussian limit fluctuations in active swimmer suspensions

Area of Science:

• Physics
• Biophysics
• Fluid Dynamics

Background:

• Swimming microorganisms create complex hydrodynamic interactions in suspensions.
• Probe particle motion in these suspensions deviates from standard Brownian motion.
• Non-Gaussian and superdiffusive dynamics are observed in active matter systems.

Purpose of the Study:

• To investigate and theoretically explain hydrodynamic fluctuations in suspensions of swimming microorganisms.
• To develop an analytical framework for non-Gaussian distributions in active systems.
• To validate the theory against experimental data from Chlamydomonas suspensions.

Main Methods:

• Observing probe particle motion in Chlamydomonas suspensions.
• Deriving an analytical theory based on summing power-law-decaying hydrodynamic interactions.
• Applying the 'physical limit operation' to model fluctuation distributions.
• Comparing theoretical predictions with experimental parameters like force generation and microorganism concentration.

Main Results:

• Probe particle fluctuations were found to be superdiffusive with non-Gaussian distributions.
• The derived analytical theory accurately describes the observed non-Gaussian distributions.
• Experimental data showed excellent agreement with the theoretical predictions.
• A master curve was observed for the time evolution of distributions, with theoretical explanations for tail behavior.

Conclusions:

• The developed theory, termed the 'physical limit operation', successfully explains non-Gaussian fluctuations in active swimmer suspensions.
• This framework extends beyond classical central limiting theory and has broad applicability.
• The study validates theoretical predictions with experimental findings in Chlamydomonas dispersions.
• The research offers a new analytical tool for understanding complex dynamics in active matter.