3,972 research outputs found
Modulational instability criteria for two-component Bose-Einstein condensates
The stability of colliding Bose-Einstein condensates is investigated. A set
of coupled Gross-Pitaevskii equations is thus considered, and analyzed via a
perturbative approach. No assumption is made on the signs (or magnitudes) of
the relevant parameters like the scattering lengths and the coupling
coefficients. The formalism is therefore valid for asymmetric as well as
symmetric coupled condensate wave states. A new set of explicit criteria is
derived and analyzed. An extended instability region, in addition to an
enhanced instability growth rate is predicted for unstable two component
bosons, as compared to the individual (uncoupled) state.Comment: 4 pages, 1 figur
Schiff Theorem and the Electric Dipole Moments of Hydrogen-Like Atoms
The Schiff theorem is revisited in this work and the residual - and
-odd electron--nucleus interaction, after the shielding takes effect, is
completely specified. An application is made to the electric dipole moments of
hydrogen-like atoms, whose qualitative features and systematics have important
implication for realistic paramagnetic atoms.Comment: 3 pages. Contribution to PANIC05, Particles and Nuclei International
Conference, Santa Fe, New Mexico, Oct. 24-28, 200
Degenerate fermion gas heating by hole creation
Loss processes that remove particles from an atom trap leave holes behind in
the single particle distribution if the trapped gas is a degenerate fermion
system. The appearance of holes increases the temperature and we show that the
heating is (i) significant if the initial temperature is well below the Fermi
temperature , and (ii) increases the temperature to
after half of the system's lifetime, regardless of the initial temperature. The
hole heating has important consequences for the prospect of observing
Cooper-pairing in atom traps.Comment: to be published in PR
Fermi-Bose quantum degenerate ^40 K - ^87 Rb mixture with attractive interaction
We report on the achievement of simultaneous quantum degeneracy in a mixed
gas of fermionic ^40 K and bosonic ^87 Rb. Potassium is cooled to 0.3 times the
Fermi temperature by means of an efficient thermalization with evaporatively
cooled rubidium. Direct measurement of the collisional cross-section confirms a
large interspecies attraction. This interaction is shown to affect the
expansion of the Bose-Einstein condensate released form the magnetic trap,
where it is immersed in the Fermi sea.Comment: 5 pages, 4 figures, replaced one figure plus some change
A microscopic quantum dynamics approach to the dilute condensed Bose gas
We derive quantum evolution equations for the dynamics of dilute condensed
Bose gases. The approach contains, at different orders of approximation, for
cases close to equilibrium, the Gross Pitaevskii equation and the first order
Hartree Fock Bogoliubov theory. The proposed approach is also suited for the
description of the dynamics of condensed gases which are far away from
equilibrium. As an example the scattering of two Bose condensates is discussed.Comment: 8 pages, submitted to Phys. Rev.
Chiral two-pion exchange and proton-proton partial-wave analysis
The chiral two-pion exchange component of the long-range pp interaction is
studied in an energy-dependent partial-wave analysis. We demonstrate its
presence and importance, and determine the chiral parameters c_i (i=1,3,4). The
values agree well with those obtained from pion-nucleon amplitudes.Comment: 13 pages, no figure
Elementary excitations in trapped Bose gases beyond mean field approximation
Using hydrodynamic theory of superfluids and the Lee-Huang-Yang equation of
state for interacting Bose gases we derive the first correction to the
collective frequencies of a trapped gas, due to effects beyond mean field
approximation. The corresponding frequency shift, which is calculated at zero
temperature and for large N, is compared with other corrections due to finite
size, non-linearity and finite temperature. We show that for reasonable choices
of the relevant parameters of the system, the non-mean field correction is the
leading contribution and amounts to about 1%. The role of the deformation of
the trap is also discussed.Comment: 4 pages, 1 Postscript figur
The Nucleon-Mass Difference in Chiral Perturbation Theory and Nuclear Forces
A new method is developed for treating the effect of the neutron-proton mass
difference in isospin-violating nuclear forces. Previous treatments utilized an
awkward subtraction scheme to generate these forces. A field redefinition is
used to remove that mass difference from the Lagrangian (and hence from
asymptotic nucleon states) and replace its effect by effective interactions.
Previous calculations of static Class II charge-independence-breaking and Class
III charge-symmetry-breaking potentials are verified using the new scheme,
which is also used to calculate Class IV nuclear forces. Two-body forces of the
latter type are found to be identical to previously obtained results. A novel
three-body force is also found. Problems involving Galilean invariance with
Class IV one-pion-exchange forces are identified and resolved.Comment: 20 pages, 2 figures, latex - submitted to Physical Review
Formation of Pairing Fields in Resonantly Coupled Atomic and Molecular Bose-Einstein Condensates
In this paper, we show that pair-correlations may play an important role in
the quantum statistical properties of a Bose-Einstein condensed gas composed of
an atomic field resonantly coupled with a corresponding field of molecular
dimers. Specifically, pair-correlations in this system can dramatically modify
the coherent and incoherent transfer between the atomic and molecular fields.Comment: 4 pages, 4 figure
Deep-water flow over the Lomonosov Ridge in the Arctic Ocean
Author Posting. © American Meteorological Society, 2005. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 35 (2005): 1489–1493, doi:10.1175/JPO2765.1.The Arctic Ocean likely impacts global climate through its effect on the rate of deep-water formation and the subsequent influence on global thermohaline circulation. Here, the renewal of the deep waters in the isolated Canadian Basin is quanitified. Using hydraulic theory and hydrographic observations, the authors calculate the magnitude of this renewal where circumstances have thus far prevented direct measurements. A volume flow rate of Q = 0.25 ± 0.15 Sv (Sv ≡ 106 m3s−1) from the Eurasian Basin to the Canadian Basin via a deep gap in the dividing Lomonosov Ridge is estimated. Deep-water renewal time estimates based on this flow are consistent with 14C isolation ages. The flow is sufficiently large that it has a greater impact on the Canadian Basin deep water than either the geothermal heat flux or diffusive fluxes at the deep-water boundaries.Financial
support was provided to P. Winsor from NSF OPP-
0352628
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