Peter Litttlewood –  Dynamical phase transitions at many body exceptional point 

Seminar  – Peter Litttlewood –  Dynamical phase transitions at many body exceptional point

• Zoom Link: https://kth-se.zoom.us/j/67773156040
• Zoom ID: 677 7315 6040
  
• Date: Tuesday Dec 8
  
• Time: 4pm Stockholm time
• Abstract:
  Michel Fruchart, Ryo Hanai, Peter Littlewood, and Vincenzo Vitelli

  Spontaneous synchronization is at the core of many natural phenomena. Your heartbeat is maintained because cells contract in a synchronous wave; some bird species synchronize their motion into flocks; quantum synchronization is responsible for laser action and superconductivity. The transition to synchrony, or between states of different patterns of synchrony, is a dynamical phase transition that has much in common with conventional phase transitions of state – for example solid to liquid, or magnetism – but the striking feature of driven dynamical systems is that the components are “active”. Consequently quantum systems with dissipation and decay are described by non-Hermitian Hamiltonians, and active matter can abandon Newton’s third law and have non-reciprocal interactions. This substantially changes the character of many-degree-of-freedom dynamical phase transitions and the critical phenomena in their vicinity, since the critical point is an “exceptional point” where eigenvalues become degenerate and eigenvectors coalesce. We will illustrate this in several different systems – a Bose-Einstein condensate of polaritons, models of multicomponent active matter such as flocks of birds, generalised Kuramoto models, and others. We argue that there is a systematic theory, generalized phase diagram, and corresponding universality classes for these dynamical systems.