Complexity Colloquium: Superfluid transport of information in turning flocks of starlings
Andrea Cavagna - ISC-CNR, Rome
Reynolds Lecture Theatre, School of Earth Sciences, Wills Memorial Building
This Complexity Colloquia event is free to attend and all are welcome (including members of the public) so please let others know about it. The talk will be followed by refreshments.
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Collective decision-making in biological systems requires all individuals in the group to go through a behavioural change of state. During this transition, the efficiency of information transport is a key factor to prevent cohesion loss and preserve robustness. The precise mechanism by which natural groups achieve such efficiency, though, is currently not fully understood.
I will present an experimental study of starling flocks performing collective turns in the field. We find that the information to change direction propagates across the flock linearly in time with negligible attenuation, hence keeping group decoherence to a minimum. This result contrasts with current theories of collective motion, which predict a slower and dissipative transport of directional information.
We have proposed a novel theory whose cornerstone is the existence of a conserved spin current generated by the gauge symmetry of the system. The theory turns out to be mathematically identical to that of superfluid transport in liquid helium and it explains the dissipationless propagating mode observed in turning flocks.
Superfluidity also provides a quantitative expression for the speed of propagation of the information, according to which transport must be swifter the stronger the group's orientational order. This prediction is verified by the data.
We argue that the link between strong order and efficient decision-making required by superfluidity may be the adaptive drive for the high degree of behavioural polarization observed in many living groups.
The mathematical equivalence between superfluid liquids and turning flocks is a compelling demonstration of the far-reaching consequences of symmetry and conservation laws across different natural systems.
If you have any queries please get in touch with the Bristol Centre for Complexity Sciences (BCCS) Manager, Matthew Guppy.