873 research outputs found
Time-dependent Gross-Pitaevskii equation for composite bosons as the strong-coupling limit of the fermionic BCS-RPA approximation
The linear response to a space- and time-dependent external disturbance of a
system of dilute condensed composite bosons at zero temperature, as obtained
from the linearized version of the time-dependent Gross-Pitaevskii equation, is
shown to result also from the strong-coupling limit of the time-dependent BCS
(or broken-symmetry RPA) approximation for the constituent fermions subject to
the same external disturbance. In this way, it is possible to connect
excited-state properties of the bosonic and fermionic systems by placing the
Gross-Pitaevskii equation in perspective with the corresponding fermionic
approximationsComment: 4 pages, 1 figur
Non-Linear/Non-Commutative Non-Abelian Monopoles
Using recently proposed non-linearly realized supersymmetry in non-Abelian
gauge theory corrected to the order (alpha')^2, we derive the non-linear BPS
equations in the background B-field for the U(2) monopoles and instantons. We
show that these non-Abelian non-linear BPS equations coincide with the
non-commutative anti-self-dual equations via the Seiberg-Witten map.Comment: 9 pages, LaTe
Semiclassical Solution of the Quantum Hydrodynamic Equation for Trapped Bose-condensed Gas in the l=0 Case
In this paper the quantum hydrodynamic equation describing the collective,
low energy excitations of a dilute atomic Bose gas in a given trapping
potential is investigated with the JWKB semiclassical method. In the case of
spherically symmetric harmonic confining potential a good agreement is shown
between the semiclassical and the exact energy eigenvalues as well as wave
functions. It is also demonstrated that for larger quantum numbers the
calculation of the semiclassical wave function is numerically more stable than
the exact polynomial with large alternating coefficients.Comment: 12 pages, 7 figure
Optimal Hypercontractivity for Fermi Fields and Related Non-Commutative Integration
Optimal hypercontractivity bounds for the fermion oscillator semigroup are
obtained. These are the fermion analogs of the optimal hypercontractivity
bounds for the boson oscillator semigroup obtained by Nelson. In the process,
several results of independent interest in the theory of non-commutative
integration are established. {}.Comment: 18 p., princeton/ecel/7-12-9
The non-abelian D-brane effective action through order
Requiring the existence of certain BPS solutions to the equations of motion,
we determine the bosonic part of the non-abelian D-brane effective action
through order . We also propose an economic organizational
principle for the effective action.Comment: 12 pages, 2 figures, JHEP styl
Hydrodynamic modes of a 1D trapped Bose gas
We consider two regimes where a trapped Bose gas behaves as a one-dimensional
system. In the first one the Bose gas is microscopically described by 3D mean
field theory, but the trap is so elongated that it behaves as a 1D gas with
respect to low frequency collective modes. In the second regime we assume that
the 1D gas is truly 1D and that it is properly described by the Lieb-Liniger
model. In both regimes we find the frequency of the lowest compressional mode
by solving the hydrodynamic equations. This is done by making use of a method
which allows to find analytical or quasi-analytical solutions of these
equations for a large class of models approaching very closely the actual
equation of state of the Bose gas. We find an excellent agreement with the
recent results of Menotti and Stringari obtained from a sum rule approach.Comment: 15 pages, revtex, 1 figure
Mean-field analysis of collapsing and exploding Bose-Einstein condensates
The dynamics of collapsing and exploding trapped Bose-Einstein condensat es
caused by a sudden switch of interactions from repulsive to attractive a re
studied by numerically integrating the Gross-Pitaevskii equation with atomic
loss for an axially symmetric trap. We investigate the decay rate of
condensates and the phenomena of bursts and jets of atoms, and compare our
results with those of the experiments performed by E. A. Donley {\it et al.}
[Nature {\bf 412}, 295 (2001)]. Our study suggests that the condensate decay
and the burst production is due to local intermittent implosions in the
condensate, and that atomic clouds of bursts and jets are coherent. We also
predict nonlinear pattern formation caused by the density instability of
attractive condensates.Comment: 7 pages, 8 figures, axi-symmetric results are adde
Instabilities in the two-dimensional cubic nonlinear Schrodinger equation
The two-dimensional cubic nonlinear Schrodinger equation (NLS) can be used as
a model of phenomena in physical systems ranging from waves on deep water to
pulses in optical fibers. In this paper, we establish that every
one-dimensional traveling wave solution of NLS with trivial phase is unstable
with respect to some infinitesimal perturbation with two-dimensional structure.
If the coefficients of the linear dispersion terms have the same sign then the
only unstable perturbations have transverse wavelength longer than a
well-defined cut-off. If the coefficients of the linear dispersion terms have
opposite signs, then there is no such cut-off and as the wavelength decreases,
the maximum growth rate approaches a well-defined limit.Comment: 4 pages, 4 figure
A Parton Model for Inclusive Semileptonic B Meson Decays
The parton model for semileptonic B meson decays is studied with special
attention to the decay distributions. We find that the spectra show dramatic
variations when we introduce cuts on the hadronic energy or invariant mass of
hadrons. Results for both and decays are
presented. The detailed spectra may help to separate the two types of decays.Comment: 9 pages, DO-TH 93/29, OHSTPY-HEP-T-93-011, September 199
The vacuum structure in a supersymmetric gauged Nambu-Jona-Lasinio model
The dynamical breakdown of the symmetry triggered by a
top-antitop condensate is studied in a supersymmetric version of the gauged
Nambu-Jona-Lasinio model. An effective potential approach is used to
investigate the vacuum structure and the equivalence with the minimal
supersymmetric standard model. The role of the soft supersymmetry breaking
terms is analyzed in detail in a version of the model where the electroweak
gauge interactions are turned off.Comment: 32 pages (+2 figures not included), Latex, LPTHE 93/0
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