Collective behaviour of natural swarms in 3.99 dimensions - Mattia Scandolo - Young Seminars SIFS

Collective behaviour of natural swarms in 3.99 dimensions
Mattia Scandolo, James Franck Institute - University of Chicago
Abstract: The renormalization group (RG) is one of the most powerful tools in statistical physics, allowing to infer the universal quantities characterising the collective behaviour of strongly correlated systems. Extension of the predictive power of the renormalization group to collective biological systems would greatly strengthen the effort to put physical biology on a firm basis. A crucial step in this direction has been provided by looking at the case of swarms of midges in the field. The experimental evidence of strong correlations, combined with the lack of any global order, suggests swarms are posed at the onset of a critical ordering transition, making the RG the ideal tool to account for their collective properties.
To describe swarm's collective behaviour, I will introduce a field theory which features both the active self-propelled motion of midges and their behavioural inertia, namely the resistance of midges to change their trajectory. A perturbative renormalization group analysis shows the emergence of a novel universality class, whose dynamic critical exponent is z = 1.35 in three dimensions, in good agreement with experiments (1.37 ± 0.11). These results probe the power of the renormalization group for the description of non-trivial collective behaviours in biophysics, showing how universality might play a crucial role also in the description of biological systems.
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