Universiteit Leiden

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Dissertation

Geometry and Topology in Active and Driven Systems

The key characteristic of active matter is the motion of an emergent collection (such as a flock of birds), which is driven by the consumption of energy by its active components (i.e. individual birds).

Author
Green, R.
Date
03 July 2018
Links
Thesis in Leiden Repository

The key characteristic of active matter is the motion of an emergent collection (such as a flock of birds), which is driven by the consumption of energy by its active components (i.e. individual birds). In this thesis, the central question I consider is: how do topology and geometry affect the motion of active and other driven systems?I answer this question by considering several examples. Starting with active nematics, I show that geometry can eliminate the threshold reported for such systems and demonstrate how this can be realised, which can be useful in designing laminar flows at low activity. I then construct a minimal hydrodynamic theory of a living liquid crystal, in which bacteria are controlled by nematic patterning on a substrate which exhibit non-trivial topology. Finally I investigate topological mechanical chains; after explaining the different phases of the chain, in the process uncovering a new superspinner phase, I go on to analyse how these chains swim at low Reynolds number, and find that this is connected to both the topology and geometry of the chain.

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