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SUMMARY:Emergent collective properties in inertial active matter - Lorenzo
  Caprini (Gran Sasso Science Institute)
DTSTART:20240130T130000Z
DTEND:20240130T140000Z
UID:TALK209737@talks.cam.ac.uk
CONTACT:Sarah Loos
DESCRIPTION:Active matter comprises autonomously propelled particles\, suc
 h as active colloids\, bacteria\, cells\, and self-propelled granular obje
 cts that convert energy from the environment into directed motion. These s
 ystems are intrinsically out of equilibrium and are characterized by self-
 organization and fascinating collective phenomena. At the micron scale\, t
 ypical of overdamped dynamics\, active particles running in opposite direc
 tions block each other and show transient dynamical arrest that can promot
 e cluster nucleation and motility-induced phase separation. Here\, we expe
 rimentally and numerically investigate the dynamical clustering characteri
 zing active systems by considering externally driven granular particles\, 
 called vibrobots. As inertia increases\, we observe clustering suppression
  as well as the suppression of wetting effects at walls\, typical of micro
 swimmers. Besides\, the system shows purely inertia-induced phenomena\, su
 ch as different kinetic temperatures inside and outside the clusters as we
 ll as a solid-liquid transition in the cluster's inner structure.  Strikin
 gly\, a novel collective effect is observed: dense active systems are char
 acterized by a hidden order in the velocity field emerging in the absence 
 of torques or explicit alignment mechanisms between different particles. W
 e call this phenomenon spontaneous velocity alignment. This results in spa
 tial velocity correlations\, which we have numerically and theoretically p
 redicted\, and is due to activity-induced collective excitations which are
  waves of entropy production. 
LOCATION:Center for Mathematical Sciences\, Lecture room MR4
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