Some approaches to polaron theory

Bogolubov, N. N.

doi:10.1007/bf00733225

Cited by 52 publications

(91 citation statements)

References 11 publications

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“…(4), we obtain the total nuclear fusion rate R per unit volume per unit time ( ) We note a very important fact that R does not depend on the Gamow factor in contrast to the conventional theory for nuclei fusion in free space. This is consistent with the conjecture noted by Dirac [23] and used by Bogolubov [26] that boson creation and annihilation operators can be treated simply as numbers when the ground state occupation number is large. This implies that for large N each charged boson behaves as an independent particle in a common average background potential and the Coulomb interaction between two charged bosons is suppressed.…”

Section: Total Fusion Rate and Theoretical Predictionssupporting

confidence: 91%

Quantum Many-Body Theory and Mechanisms for Low Energy Nuclear Reaction Processes in Matter

Kim

2004

Prog. Theor. Phys. Suppl.

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Section: Total Fusion Rate and Theoretical Predictionssupporting

confidence: 91%

Quantum Many-Body Theory and Mechanisms for Low Energy Nuclear Reaction Processes in Matter

Kim

2004

Prog. Theor. Phys. Suppl.

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“…Then Eq. (27) gives T, &10'm»m . (30) Given this set of chosen values for So, N, ff, and the upper limit of Q in (29), Eq.…”

Section: ' N Ttmentioning

confidence: 98%

Ultrarelativistic Bose-Einstein condensation in the Einstein universe and energy conditions

Parker

Zhang

1991

Phys. Rev. D

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We study a relativistic boson gas of particles and antiparticles in the Einstein universe at high temperatures and densities. We obtain the thermodynamic potential of the boson system in curved spacetime.The result shows that ultrarelativistic Bose-Einstein condensation can occur at very high densities in the Einstein universe, and by implication in the early stages of a dynamically changing universe. We show that in a slowly changing universe with a weak self-interaction this ultrarelativistic Bose-Einstein condensate would violate the strong energy condition which enters into the cosmological singularity theorem s.

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“…Because a , 0, the effective interaction between atoms is attractive, and the BEC phenomenon is substantially altered. Attractive interactions were long believed to make a condensate unstable and thus prevent BEC [1,2], but it is now known that, for a confined gas, a metastable condensate can exist as long as its occupation number, N 0 , remains small [3]. Such condensates are predicted to be rich in physics, exhibiting properties such as solitonlike behavior [4] and macroscopic quantum tunneling [5].…”

mentioning

confidence: 99%

Measurements of Collective Collapse in a Bose-Einstein Condensate with Attractive Interactions

et al. 1999

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The occupation number of a magnetically trapped Bose-Einstein condensate is limited for atoms with attractive interactions. It has been predicted that, as this limit is approached, the condensate will collapse by a collective process. The measured spread in condensate number for samples of 7 Li atoms undergoing thermal equilibration is consistent with the occurrence of such collapses. [ S0031-9007(98) The attainment of Bose-Einstein condensation (BEC) in dilute atomic gases has provided a new domain for studying the nonlinear effects of interactions in thermodynamic systems. Among the gases in which BEC has been observed, 7 Li is unique in having a negative triplet s-wave scattering length a. Because a , 0, the effective interaction between atoms is attractive, and the BEC phenomenon is substantially altered. Attractive interactions were long believed to make a condensate unstable and thus prevent BEC [1,2], but it is now known that, for a confined gas, a metastable condensate can exist as long as its occupation number, N 0 , remains small [3]. Such condensates are predicted to be rich in physics, exhibiting properties such as solitonlike behavior [4] and macroscopic quantum tunneling [5]. In particular, complex dynamical behavior is expected as N 0 approaches its stability limit [6][7][8]. In this Letter, we describe experimental investigations of this behavior.Attractive interactions limit N 0 because, at a maximum number N m , the compressibility of the condensate becomes negative and it will implosively collapse. By equating the positive zero-point kinetic energy to the negative interaction energy, it is found that N m ϳ ᐉ͞jaj when the condensate is confined to volume ᐉ 3 . The stability limit is more precisely determined from numerical solution of the nonlinear Schrödinger equation (NLSE) [9]. For 7 Li in our magnetic trap, a 21.46 nm [10] and ᐉ ഠ 3 mm, which yield a stability limit of ϳ1250 atoms.As the gas is cooled below the critical temperature for BEC, N 0 grows until N m is reached. The condensate then collapses spontaneously if N 0 $ N m , or the collapse can be initiated by thermal fluctuations or quantum tunneling for N 0 & N m [5,7]. During the collapse, the condensate shrinks on the time scale of the trap oscillation period. As the density rises, the rates for inelastic collisions such as dipolar decay and three-body molecular recombination increase. These processes release sufficient energy to immediately eject the colliding atoms from the trap, thus reducing N 0 . The ejected atoms are very unlikely to further interact with the gas before leaving the trap, since the density of noncondensed atoms is low. As the collapse proceeds, the collision rate grows quickly enough that the density remains small compared to jaj 23 and the condensate remains a dilute gas [7,8].Both the collapse and the initial cooling process displace the gas from thermal equilibrium. As long as N 0 is smaller than its equilibrium value, as determined by the total number and average energy of the trapped atoms, the condensate...

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Some approaches to polaron theory

Cited by 52 publications

References 11 publications

Quantum Many-Body Theory and Mechanisms for Low Energy Nuclear Reaction Processes in Matter

Quantum Many-Body Theory and Mechanisms for Low Energy Nuclear Reaction Processes in Matter

Ultrarelativistic Bose-Einstein condensation in the Einstein universe and energy conditions

Measurements of Collective Collapse in a Bose-Einstein Condensate with Attractive Interactions

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