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SUMMARY:Theories of Active Phase Separation - Mike Cates (University of Ca
 mbridge)
DTSTART:20230707T080000Z
DTEND:20230707T090000Z
UID:TALK201178@talks.cam.ac.uk
DESCRIPTION:Active materials\, like passive ones\, can undergo phase separ
 ation into regions of higher and lower particle density divided by a sharp
  interface. In the passive case\, there are long established field theorie
 s for such phase separations which must respect the underlying time-revers
 al symmetry of dynamics in systems close to thermal equilibrium. In active
  systems\, this symmetry is broken\, and new terms need to be added to suc
 h models which can entirely change their behaviour. One striking example i
 s that the Ostwald process\, in which phase separation proceeds by growth 
 of large droplets at the expense of smaller ones\, can go into reverse. Th
 is happens when one of several interfacial tensions (all of which coincide
  in the passive case) becomes negative\, and leads to incomplete phase sep
 aration exhibiting clusters or bubbles. At higher activity\, a second tens
 ion\, governing capillary fluctuations\, can also become negative\; the re
 sulting instability leads instead to an 'active foam' phase. In systems wh
 ere all relevant interfacial tensions remain positive\, activity can still
  lead to major effects. Specifically\, (i) the rate of droplet nucleation\
 , which&nbsp\;(remarkably) can be calculated via an active counterpart of 
 Classical Nucleation Theory\, depends exponentially on active parameters a
 s well as passive ones\; and (ii) activity changes the universality class 
 and scaling exponents for dynamical roughening of an interface between pha
 ses via buildup of capillary waves.
LOCATION:Seminar Room 1\, Newton Institute
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