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SUMMARY:From active liquids to active solids: a tale of criticality\, phas
 e transitions and phase separations - Thibault Bertrand\, Imperial College
  London
DTSTART:20220531T120000Z
DTEND:20220531T130000Z
UID:TALK173105@talks.cam.ac.uk
CONTACT:Camille Scalliet
DESCRIPTION:Active matter provides a fertile ground for discovering novel 
 physics. Active systems display a wealth of emergent phenomena which are n
 ot found in equilibrium systems. For active liquids\, previous works obser
 ved: motility-induced phase separation (MIPS)\, long-ranged ordered (colle
 ctive motion) phase in two dimensions\, and order-disorder phase co-existe
 nces (banding and reverse-banding regimes). In the first part of this talk
 \, I will show how we unify these diverse phase transitions and phase co-e
 xistences into a single formulation based on generic hydrodynamic equation
 s for polar active fluids. In doing so\, we reveal the existence of a nove
 l co-moving phase co-existence and of a novel multicritical point. In the 
 second part of the talk\, I will consider very dense active systems. In re
 cent years\, much progress has been made in the understanding of the so-ca
 lled athermal jamming transition\, a rigidity transition particulate matte
 r generically undergo as their volume fraction is increased. However\, our
  current understanding of active jamming is crucially lacking. While it is
  natural to expect that applying high enough self-propulsion forces to ini
 tially passive jammed systems will result into unjamming of the systems\, 
 what kind of universal behavior (if any) is observed around the athermal c
 ritical jamming point when active or thermal fluctuations are added remain
 s unknown. By means of numerical simulations and mean-field analytical arg
 uments\, we probe the effect of 1) persistent active and 2) thermal fluctu
 ations on a dense\, athermal jammed system of spheres in 2D and ask the qu
 estion of whether a strictly jammed system (understood as remaining above 
 isostaticity) exists at non-zero fluctuations strengths. We uncover critic
 al behaviour in the vicinity of the athermal jamming critical point which 
 is strikingly independent of the type of perturbation (active or thermal).
  
LOCATION:Center for Mathematical Sciences\, Lecture room MR4
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