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TZID:Europe/Paris
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BEGIN:VEVENT
UID:0-609@lptms.universite-paris-saclay.fr
DTSTART:20180605T110000Z
DTEND:20180605T120000Z
DTSTAMP:20180529T053815Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/seminaire-du-lptm
 s-serguey-andreev-seminaire-exceptionnel/
SUMMARY:Séminaire du LPTMS: Serguey Andreev - LPTMS\, salle 201\, 2ème é
 tage\, Bât 100\, Campus d'Orsay - 5 Juin 18 11:00
DESCRIPTION:Effective interactions in a quantum Bose-Bose mixture\nSerguey 
 Andreev\, ITMO University\, St. Petersburg\, Russia\nApplication of the me
 thods of Quantum Electrodynamics (QED) to a system of bosons at absolute z
 ero temperature put forward by Spartak Beliaev in 1958 has been one of the
  most powerful analytical methods in studies of Bose-Einstein condensates.
  The Beliaev theory provides a prescription of replacement of the actual m
 icroscopic interaction by an effective potential which can be used for per
 turbative expansion of the many-body Hamiltonian. Originally designed for 
 one-component systems\, the method has recently been applied to binary Bos
 e mixtures in the context of supersolidity and stabilization of collapsing
  Bose-Einstein condensates by quantum fluctuations. The present work is ai
 med at investigation of legitimacy of extrapolation of the Beliaev prescri
 ption to two-component systems. We show that quantum scatterings of differ
 ent components\, which until now have been assumed independent\, can inter
 fere due to the Andreev-Bashkin entrainment effect. The effect manifests i
 tself in renormalization of the elementary excitations of the system. This
  result has escaped the earlier considerations based on the Fourier expans
 ion of small-amplitude oscillations of the order parameter. We explain how
  one can account for the effect by using a properly generalized Bogoliubov
  approach. In 3D the effect appears in the second order of the perturbatio
 n theory\, which makes possible using the concept of effective potential i
 n this case. The entrainment arises due to "dressing" of magnons with Bogo
 liubov phonon modes\, by analogy with the physics of Bose polaron. We expl
 oit this fruitful analogy to speculate on possible formation of a magnon c
 rystal in the strongly-interacting regime.
LOCATION:LPTMS\, salle 201\, 2ème étage\, Bât 100\, Campus d'Orsay\, 15 
 Rue Georges Clemenceau\, Orsay\, 91405\, France
GEO:48.698185;2.181768
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\,
  Orsay\, 91405\, France;X-APPLE-RADIUS=100;X-TITLE=LPTMS\, salle 201\, 2è
 me étage\, Bât 100\, Campus d'Orsay:geo:48.698185,2.181768
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