Random walks are a cornerstone of statistical physics. While Brownian motion has long been under scrutiny, there is a growing interest in a different type of motion: persistent walks. Examples abound in active matter and biological world, from self-propelled particles and crawling cells to foraging animals and a plethora of swimming micro-organisms. The statistical properties of such
random motions are often unknown yet they play a key role in many vital functions of the organisms and ultimately in their survival.
One striking instance of persistent random motion is the
run-and-tumble of bacteria. Bouts of persistent motion ("run") are interspersed with sudden changes of direction ("tumble"). Recent research reveals that bacteria display a fascinating repertoire of swimming patterns, which differ in their run and tumble characteristics. Why? Which benefits come with each swimming strategy?
The goal of the internship is to understand theoretically the statistical properties of run-and-tumble in complex environments such as porous disordered media. Recent findings suggest a
universal character in the dispersal phenomenon, that remains to be understood. To address this question, you will use a combination of numerical
simulations and
theoretical modelling.
There are many facets of swimming strategies that can be explored in a
PhD thesis. These include transport under external field and rectification in anisotropic materials. Besides, optimization of informed swimming strategies, where the strategy is adapted dynamically, remains mostly unexplored. Finally, collective effects, such as clustering and clogging, in assemblies of persistent random walkers, also deserve some investigation.
The ideal candidate would have a strong background in statistical physics and soft or active matter. No background in biology is required.
Keywords:
statistical physics, active matter, random walks, micro-organisms.
Contact: François Detcheverry
francois.detcheverry@univ-lyon1.fr
Team Liquides et Interfaces, Institut Lumière Matière (Lyon)
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