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SUMMARY:Critical properties of active phase-separation and entropy product
 ion. - Fernando Caballero\, University of California Santa Barbara
DTSTART:20210518T150000Z
DTEND:20210518T160000Z
UID:TALK159673@talks.cam.ac.uk
CONTACT:Camille Scalliet
DESCRIPTION:UNUSUAL TIME (4pm)!\n\nZoom link: https://maths-cam-ac-uk.zoom
 .us/j/94018037756\n\nThe critical properties of active phase separation ha
 ve been studied numerically\, finding Ising-like transitions between unifo
 rm and phase separated states\, relegating their universal behaviour to th
 at of a passive system. There are\, though\, transitions to other micropha
 se separated phases which have not been studied from the point of view of 
 their critical properties in depth\, specially numerically. This talk will
  review some analytical results about all these transitions and their diff
 erences. The first half of the talk will review a minimal extension of Mod
 el B\, typically used to model diffusive binary phase separation\, that br
 eaks time reversal symmetry. We will see that this simple continuum theory
  displays these different phases seen in particle simulations and some exp
 erimental systems\, and that a standard Renormalization Group analysis pro
 perly captures the Ising transition\, as well as new transitions into a st
 rong coupling regime\, producing a phase diagram that matches one found nu
 merically. The second half of the talk will introduce the entropy producti
 on for this continuum model\, and we will see some more recent result abou
 t its critical behaviour\, applying a similar scaling anaysis to it. The r
 esult\, counterintuitive at first\, is that the entropy production per cor
 relation volume at the Ising transition stays constant at mean field level
 \, and can potentially diverge at the critical point. This is surprising s
 ince at that critical point all active parameters of the theory are irrele
 vant from the scaling perspective\, so its behaviour is equilibrium-like a
 t large scales\, meaning there is no equilibrium observable that we could 
 measure on the system that would differentiate between the active and pass
 ive transitions. Since this result comes from evaluating the entropy produ
 ction operator at an equilibrium critical point\, this means that its dive
 rgence is a property of the equilibrium Ising transition\, only for a quan
 tity that is strictly zero at equilibrium\, thus indicating that entropy p
 roduction propagates to all scales as long as it is non zero\, no matter h
 ow close to equilibrium the system is.
LOCATION:via zoom\, meeting ID 940-1803-7756
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