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SUMMARY:Glassy Dynamics and Jamming in Dense Persistent Active Matter - Ch
 andan Dasgupta (Indian Institute of Science)
DTSTART:20231121T110000Z
DTEND:20231121T120000Z
UID:TALK208402@talks.cam.ac.uk
DESCRIPTION:In several biological systems\, such as bacterial cytoplasm\, 
 cytoskeleton-motor complexes and epithelial sheets of cells\, self-propuls
 ion or activity is found to fluidize a glassy state that exhibits characte
 ristic glassy features in the absence of activity. Recent experiments on d
 ense systems of Janus colloids and vibrated granular systems have provided
  a lot of information about how activity affects glassy dynamics and jammi
 ng. To develop a theoretical understanding of these non-equilibrium phenom
 ena\, we have studied\, using molecular dynamics and Brownian dynamics sim
 ulations\, the effects of activity in several model glass-forming liquids.
  The activity in these systems is characterized by two parameters: the mag
 nitude of the active force and its persistence time. If the persistence ti
 me is short\, then the observed behaviour is similar to that near the usua
 l glass transition. The introduction of activity reduces the glass transit
 ion temperature and decreases the kinetic fragility. Some of these effects
  can be understood from a generalization of the Random First Order Transit
 ion (RFOT) theory of the glass transition to active systems. For large but
  finite persistence times\, the approach to dynamical arrest at low propul
 sion force goes through a phase characterized by intermittency. This inter
 mittency is a consequence of long periods of jamming followed by bursts of
  plastic yielding\, akin to the response of dense amorphous solids to an e
 xternally imposed shear. In the limit of infinite persistence time\, the h
 omogeneous liquid state obtained at large values of the active force exhib
 its several unusual properties: the average kinetic energy increases with 
 increasing system size and a length scale extracted from spatial velocity 
 correlations increases with system size as a power law with exponent close
  to one. This active liquid evolves to a force-balanced jammed state when 
 the self-propulsion force is decreased below a threshold value. The jammin
 g proceeds via a three-stage relaxation process whose timescale grows with
  the magnitude of the active force and the system size. We relate the depe
 ndence on the system size to the large correlation length observed in the 
 liquid state. Some of the properties of the jammed state obtained for smal
 l active force are found to be substantially different from those of passi
 ve jammed systems.
LOCATION:Seminar Room 2\, Newton Institute
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