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SUMMARY:Non-reciprocal phase transitions - Peter Littlewood (The Universit
 y of Chicago)
DTSTART:20251008T151500Z
DTEND:20251008T161500Z
UID:TALK235597@talks.cam.ac.uk
CONTACT:Andrea Pizzi
DESCRIPTION:Spontaneous synchronization is at the core of many natural phe
 nomena. Your heartbeat is maintained because cells contract in a synchrono
 us wave\; some bird species synchronize their motion into flocks\; quantum
  synchronization is responsible for laser action and superconductivity. Th
 e transition to synchrony\, or between states of different patterns of syn
 chrony\, is a dynamical phase transition that has much in common with conv
 entional phase transitions of state – for example solid to liquid\, or m
 agnetism – but the striking feature of driven dynamical systems is that 
 the components are “active”. Consequently quantum systems with dissipa
 tion and decay are described by non-Hermitian Hamiltonians\, and active ma
 tter can abandon Newton’s third law and have non-reciprocal interactions
 . This substantially changes the character of many-degree-of-freedom dynam
 ical phase transitions between synchronized steady states and the critical
  phenomena in their vicinity\, since the critical point is an “exception
 al point” where eigenvalues become degenerate and eigenvectors coalesce.
  We will illustrate this in several different systems – a Bose-Einstein 
 condensate of polaritons\, models with cavity mediated interactions\, and 
 models of multicomponent active matter such as flocks of birds\, generaliz
 ed Kuramoto models\, and Wilson-Cowan models of neural networks. We argue 
 that there is a systematic theory and generalized phase diagram\, and corr
 esponding universality behaviors determined by the symmetry of the models.
LOCATION:Lecture Teatre\, Ray Dolby Centre
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