Abstracts of papers deposited at VINITI

Popov, L. E.; Sharkeev, Yu. P.; Koneva, N. A.; Esipenko, V. F.; Popov, V. L.; Brylikhanov, A. A.; Sergeev, V. L.; Timoshinin, V. S.; Lobikov, E. A.; Iremadze, S. G.; Kim, A. S.; Annenikov, Yu. M.; Balbakov, D.; Pichugin, V. F.; Memnonov, V. P.; Bagrov, V. G.; Bukhbinder, I. L.; Gitman, D. M.; Pavlov, P. M.; Tsaune, A. Ya.; Golovchenko, E. I.; Botakin, A. A.; Salev, A. V.; Sharko, A. V.; Shukhovarov, V. F.; Seregin, G. V.; Denisov, D. A.; Knyazev, D. A.; Vafin, R. A.; Cheremisin, V. P.; Galishev, V. S.; Shapiro, M. M.; Volkov, L. A.; Demchenko, A. M.; Maronchuk, I. E.; Kuchumov, B. M.; Sal'man, E. G.; Vertoprakhov, V. N.; Grigorev, Artur; Bakhyshov, A. E.; Akhmedov, A. M.; Rzaev, L. A.; Guseinov, G. D.; Gridchin, V. A.; Osintseva, L. A.; Kalinenko, D. I.; Sonchik, U. K.; Kovalevskaya, M. P.; Minchenko, L. S.; Kulikov, V. A.; Fatkullin, O. Kh.; Popov, D. S.; Annenkov, Yu. M.; Korablev, G. A.; Mastov, Sh. R.

doi:10.1007/bf01207708

Cited by 2 publications

(3 citation statements)

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“…The summation over these states includes the noninteracting ground state. 10 In the homogeneous limit, the scattering between states with relative momentumhk andhk ′ is independent of the centre-of-mass momentumhK and is described by the matrix element T 2b (k ′ , k, z) = k ′ K|T 2b (z)|k K . Physical scattering events correspond to on-shell matrix elements for which k = k ′ and z = lim η→0 ǫ sp k + ıη (here k = |k|, ǫ sp k =h 2 k 2 /2m,m = m/2 is the reduced mass, and we have redefined z to include the centre-of-mass energy).…”

Section: A the Two-body T-matrixmentioning

confidence: 99%

“…In 1958, Beliaev introduced a theory of BEC at T = 0 based on the Green's functions of quantum field theory [8]. This approach was further developed by Popov and Fadeev [9,10] who applied it to calculations at finite temperature, and recently Fedichev and Shlyapnikov [11] have extended the calculations to higher order and to trapped gases. A similar approach (but restricted to the homogeneous limit) has also been described by Shi and Griffin [12].…”

Section: Introductionmentioning

confidence: 99%

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A gapless theory of Bose-Einstein condensation in dilute gases at finite temperature

Morgan

2000

J. Phys. B: At. Mol. Opt. Phys.

139

302

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In this paper we develop a gapless theory of BEC which can be applied to both trapped and homogeneous gases at zero and finite temperature. The starting point for the theory is the second quantized, many-body Hamiltonian for a system of structureless bosons with pairwise interactions. A number conserving approach is used to rewrite this Hamiltonian in a form which is approximately quadratic with higher order cubic and quartic terms. The quadratic part of the Hamiltonian can be diagonalized exactly by transforming to a quasiparticle basis, while requiring that the condensate satisfy the Gross-Pitaevskii equation. The non-quadratic terms are assumed to have a small effect and are dealt with using first and second order perturbation theory. The conventional treatment of these terms, based on factorization approximations, is shown to be inconsistent.Infra-red divergences can appear in individual terms of the perturbation expansion, but we show analytically that the total contribution beyond quadratic order is finite. The resulting excitation spectrum is gapless and the energy shifts are small for a dilute gas away from the critical region, justifying the use of perturbation theory. Ultra-violet divergences can appear if a contact potential is used to describe particle interactions. We show that the use of this potential as an approximation to the two-body T-matrix leads naturally to a high-energy renormalization.The theory developed in this paper is therefore well-defined at both low and high energy and provides a systematic description of Bose-Einstein condensation in dilute gases. It can therefore be used to calculate the energies and decay rates of the excitations of the system at temperatures approaching the phase transition.

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Section: A the Two-body T-matrixmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A gapless theory of Bose-Einstein condensation in dilute gases at finite temperature

Morgan

2000

J. Phys. B: At. Mol. Opt. Phys.

139

302

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“…The secondorder correction to the Bogoliubov energy spectrum was given by Beliaev [1], who developed a diagrammatic Green's function approach to describe the energy spectrum of elementary excitations at absolute zero [2]. Afterwards, finite-temperature theories based on the Beliaev technique were developed for weakly interacting Bose gases [10,16,17,18]. With the rapid development of techniques for precise measurements of physical observables, the small effect of quantum depletion is no longer beyond the scope of experimenters.…”

Section: Introductionmentioning

confidence: 99%

Beliaev theory of spinor Bose–Einstein condensates

2013

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By generalizing the Green's function approach proposed by Beliaev [1,2], we investigate the effect of quantum depletion on the energy spectra of elementary excitations in an F = 1 spinor Bose-Einstein condensate, in particular, of 87 Rb atoms in an external magnetic field. We find that quantum depletion increases the effective mass of magnons in the spin-wave excitations with quadratic dispersion relations. The enhancement factor turns out to be the same for both ferromagnetic and polar phases, and also independent of the magnitude of the external magnetic field. The lifetime of these magnons in a 87 Rb spinor BEC is shown to be much longer than that of phonons. We propose an experimental setup to measure the effective mass of these magnons in a spinor Bose gas by exploiting the effect of a nonlinear dispersion relation on the spatial expansion of a wave packet of transverse magnetization. This type of measurement has practical applications, for example, in precision magnetometry.

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Abstracts of papers deposited at VINITI

Cited by 2 publications

References 0 publications

A gapless theory of Bose-Einstein condensation in dilute gases at finite temperature

A gapless theory of Bose-Einstein condensation in dilute gases at finite temperature

Beliaev theory of spinor Bose–Einstein condensates

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