Quenched coupling, entangled equilibria, and correlated composite operators: a tale of two O(N) models

  • Souvik Banerjee
  • Julius Engelsöy
  • Jorge Larana-Aragon
  • Bo Sundborg
  • Larus Thorlacius
  • Nico WintergerstEmail author
Open Access
Regular Article - Theoretical Physics


A macroscopic version of Einstein-Podolsky-Rosen entanglement is obtained by quenching a quadratic coupling between two O(N) vector models. A quench of the mixed vacuum produces an excited entangled state, reminiscent of purified thermal equilibrium, whose properties can be studied analytically in the free limit of the individual field theories. The decoupling of different wavelength modes in free field theory prevents true thermalisation but a more subtle difference is that the density operator obtained by a partial trace does not commute with the post-quench Hamiltonian. Generalized thermal behaviour is obtained at late times, in the limit of weak initial mixing or a smooth but rapid quench. More surprisingly, late-time correlation functions of composite operators in the post-quench free field theory share interesting properties with correlators in strongly coupled systems. We propose a holographic interpretation of our result.


AdS-CFT Correspondence Effective Field Theories Holography and condensed matter physics (AdS/CMT) 


Open Access

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Copyright information

© The Author(s) 2019

Authors and Affiliations

  1. 1.Department of Physics and AstronomyUppsala UniversityUppsalaSweden
  2. 2.The Oskar Klein Centre for Cosmoparticle Physics & Department of PhysicsStockholm UniversityStockholmSweden
  3. 3.University of Iceland, Science InstituteReykjavikIceland
  4. 4.The Niels Bohr InstituteUniversity of CopenhagenCopenhagen ØDenmark

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