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BEGIN:VEVENT
UID:1-382@lptms.universite-paris-saclay.fr
DTSTART:20151028T140000Z
DTEND:20151028T163000Z
DTSTAMP:20151023T112249Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/soutenance-de-the
 se-andrii-gudyma/
SUMMARY:Soutenance de thèse : Andrii Gudyma -  - 28 Oct 15 14:00
DESCRIPTION:\nNon-equilibrium dynamics of a trapped one-dimensional Bose ga
 s\n\nAndrii Gudyma\n\nA study of breathing oscillations of a one-dimension
 al trapped interacting Bose gas is presented. Oscillations are initiated b
 y an instantaneous change of the trapping frequency. In the thesis a 1D qu
 antum Bose gas in a parabolic trap at zero temperature is considered\, and
  it is explained\, analytically and numerically\, how the oscillation freq
 uency depends on the number of particles\, their repulsive interaction\, a
 nd the trap parameters. We have focused on the many-body spectral descript
 ion\, using the sum rules approximation.  The oscillation frequency is id
 entified as the energy difference between the ground state and a particula
 r excited state.\nThe existence of three regimes is demonstrated\, namely 
 the Tonks regime\, the Thomas-Fermi regime and the Gaussian regime. The tr
 ansition from the Tonks to the Thomas-Fermi regime is described in the ter
 ms of the local density approximation (LDA). For the description of the tr
 ansition from the Thomas-Fermi to the Gaussian regime the Hartree approxim
 ation is used. In both cases the parameters where the transitions happen a
 re found. The extensive diffusion Monte Carlo simulations for a gas contai
 ning up to N = 25 particles is performed. As the number of particles incre
 ases\, predictions from the simulations converge to the ones from the Hart
 ree and LDA in the corresponding regimes. This makes the results for the b
 reathing mode frequency applicable for arbitrary values of the particle nu
 mber and interaction. The analysis is completed with the finite N perturba
 tive results in the limiting cases. The theory predicts the reentrant beha
 vior of  the breathing mode frequency when moving from the Tonks to the G
 aussian regime and fully explains the recent experiment of the Innsbruck g
 roup.\n\n
CATEGORIES:seminars
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