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Home page > Seminars > Séminaires théorie > Theory Club Wednesday December 4 2019 at 12pm in room 646A. Mathias Casiulis: "Collective Motion without Activity".

Theory Club Wednesday December 4 2019 at 12pm in room 646A. Mathias Casiulis: "Collective Motion without Activity"

Unless otherwise stated, seminars and defences take place at 11:30 in room 454A of Condorcet building.

Collective Motion without Activity

Mathias Casiulis

Abstract: Collective motion, the macroscopic polar ordering of velocities across a system of many particles, is a hallmark of so-called active systems. In such systems, the individual ``particles’’ are able to turn some local source of energy into mechanical work, and to self-propel. Examples that come to mind are flocks of birds, schools of fish, human crowds or bacterial suspensions. However, unlike some other features of active matter, collective motion is not necessarily a direct consequence of activity. It can, in fact, be obtained as a side effect of the breaking of Galilean invariance. In my talk, I will prove this point by presenting a non-Galilean, conservative model that develops collective motion at low temperatures, due to a coupling between the velocity of each particle and an internal polarity. Using the fact that this model can be treated in an equilibrium framework, I shall discuss the domain of existence of conservative collective motion, or ``Hamiltonian flocks’’, as the temperature, density, and number of particles are tuned. Finally, I shall characterise the basic dynamics of Hamiltonian flocks, and compare it to more usual active systems.

Wednesday December 4 at 12pm in room 646A

Contact : Équipe séminaires / Seminar team - Published on / Publié le 21 November 2019

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