226 research outputs found
Counterflow in a doubly superfluid mixture of Bosons and Fermions
In this article, we calculate the friction between two counter-flowing
bosonic and fermionic super-fluids. In the limit where the boson-boson and
boson-fermion interactions can be treated within the mean-field approximation,
we show that the force can be related to the dynamical structure factor of the
fermionic component. Finally, we provide asymptotic expressions for weakly and
strongly attractive fermions and show that the damping rate obeys simple
scaling laws close to the critical velocity.Comment: Submitted to Phys. Rev.
Universal phase diagram of a strongly interacting Fermi gas with unbalanced spin populations
We present a theoretical interpretation of a recent experiment presented in
ref. \cite{Zwierlein06} on the density profile of Fermi gases with unbalanced
spin populations. We show that in the regime of strong interaction, the
boundaries of the three phases observed in \cite{Zwierlein06} can be
characterized by two dimensionless numbers and .
Using a combination of a variational treatment and a study of the experimental
results, we infer rather precise bounds for these two parameters.Comment: 4 pages, 2 figure
Capillary-gravity waves: a "fixed-depth" analysis
We study the onset of the wave-resistance due to the generation of
capillary-gravity waves by a partially immersed moving object in the case where
the object is hold at a fixed immersion depth. We show that, in this case, the
wave resistance varies continuously with the velocity, in qualitative
accordance with recent experiments by Burghelea et al. (Phys. Rev. Lett. 86,
2557 (2001)).Comment: 7 pages, 3 figures, submitted to Europhysics Letter
Vortex formation in a stirred Bose-Einstein condensate
Using a focused laser beam we stir a Bose-Einstein condensate of 87Rb
confined in a magnetic trap and observe the formation of a vortex for a
stirring frequency exceeding a critical value. At larger rotation frequencies
we produce states of the condensate for which up to four vortices are
simultaneously present. We have also measured the lifetime of the single vortex
state after turning off the stirring laser beam.Comment: 4 pages, 3 figure
An Atom Faucet
We have constructed and modeled a simple and efficient source of slow atoms.
From a background vapour loaded magneto-optical trap, a thin laser beam
extracts a continuous jet of cold rubidium atoms. In this setup, the extraction
column that is typical to leaking MOT systems is created without any optical
parts placed inside the vacuum chamber. For detailed analysis, we present a
simple 3D numerical simulation of the atomic motion in the presence of multiple
saturating laser fields combined with an inhomogeneous magnetic field. At a
pressure of mbar, the moderate laser power of
10 mW per beam generates a jet of flux atoms/s with a
mean velocity of 14 m/s and a divergence of mrad.Comment: Submitted to EPJD. 1 TeX file (EPJ format), 7 picture
Analisis Komparasi Efektivitas Penjualan Sebelum Dan Sesudah Menggunakan Video Marketing Online Talk Fusion Di Manado
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Achieving one-dimensionality with attractive fermions
In this article we discuss the accuracy of effective one-dimensional theories
used to describe the behavior of ultracold atomic ensembles confined in quantum
wires by a harmonic trap. We derive within a fully many-body approach the
effective Hamiltonian describing this class of systems and we calculate the
beyond-mean field corrections to the energy of the ground state arising from
virtual transitions towards excited state of the confining potential. We find
that, due to the Pauli principle, effective finite-range corrections are one of
magnitude larger than effective three-body interactions.By comparing to exact
solutions of the purely 1D problem, we conclude that a 1D effective theory
provides a good description of the ground state of the system for a rather
large range of interaction parameters
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