170 research outputs found
Density Functional of a Two-Dimensional Gas of Dipolar Atoms: Thomas-Fermi-Dirac Treatment
We derive the density functional for the ground-state energy of a
two-dimensional, spin-polarized gas of neutral fermionic atoms with
magnetic-dipole interaction, in the Thomas-Fermi-Dirac approximation. For many
atoms in a harmonic trap, we give analytical solutions for the single-particle
spatial density and the ground-state energy, in dependence on the interaction
strength, and we discuss the weak-interaction limit that is relevant for
experiments. We then lift the restriction of full spin polarization and account
for a time-independent inhomogeneous external magnetic field. The field
strength necessary to ensure full spin polarization is derived.Comment: 12 pages, 4 figures, 1 tabl
Momentum-space correlations of a one-dimensional Bose gas
Analyzing the noise in the momentum profiles of single realizations of
one-dimensional Bose gases, we present the experimental measurement of the full
momentum-space density correlations ,
which are related to the two-body momentum correlation function. Our data span
the weakly interacting region of the phase diagram, going from the the ideal
Bose gas regime to the quasicondensate regime. We show experimentally that the
bunching phenomenon, which manifests itself as super-Poissonian local
fluctuations in momentum space, is present in all regimes. The quasicondensate
regime is however characterized by the presence of negative correlations
between different momenta, in contrast to Bogolyubov theory for Bose
condensates, predicting positive correlations between opposite momenta. Our
data are in good agreement with {\it ab-initio} calculations.Comment: 10 pages (including appendix
Exact density profiles and symmetry classification for strongly interacting multi-component Fermi gases in tight waveguides
We consider a mixture of one-dimensional strongly interacting Fermi gases up
to six components, subjected to a longitudinal harmonic confinement. In the
limit of infinitely strong repulsions we provide an exact solution which
generalizes the one for the two-component mixture. We show that an imbalanced
mixture under harmonic confinement displays partial spatial separation among
the components, with a structure which depends on the relative population of
the various components. Furthermore, we provide a symmetry characterization of
the ground and excited states of the mixture introducing and evaluating a
suitable operator, namely the conjugacy class sum. We show that, even under
external confinement, the gas has a definite symmetry which corresponds to the
most symmetric one compatible with the imbalance among the components. This
generalizes the predictions of the Lieb-Mattis theorem for a fermionic mixture
with more than two components.Comment: 14 pages, 2 figures, invited contribution to special issue in NJP in
memory of Marvin Girardeau. New Journal of Physics 201
Fermionization of a strongly interacting Bose-Fermi mixture in a one-dimensional harmonic trap
We consider a strongly interacting one-dimensional (1D) Bose-Fermi mixture
confined in a harmonic trap. It consists of a Tonks-Girardeau (TG) gas (1D Bose
gas with repulsive hard-core interactions) and of a non-interacting Fermi gas
(1D spin-aligned Fermi gas), both species interacting through hard-core
repulsive interactions. Using a generalized Bose-Fermi mapping, we determine
the exact particle density profiles, momentum distributions and behaviour of
the mixture under 1D expansion when opening the trap. In real space, bosons and
fermions do not display any phase separation: the respective density profiles
extend over the same region and they both present a number of peaks equal to
the total number of particles in the trap. In momentum space the bosonic
component has the typical narrow TG profile, while the fermionic component
shows a broad distribution with fermionic oscillations at small momenta. Due to
the large boson-fermion repulsive interactions, both the bosonic and the
fermionic momentum distributions decay as at large momenta, like in
the case of a pure bosonic TG gas. The coefficient is related to the
two-body density matrix and to the bosonic concentration in the mixture. When
opening the trap, both momentum distributions "fermionize" under expansion and
turn into that of a Fermi gas with a particle number equal to the total number
of particles in the mixture.Comment: revised version; 8 pages, 7 figure
Continuous Cold-atom Inertial Sensor with Rotation Stability
We report the operation of a cold-atom inertial sensor which continuously
captures the rotation signal. Using a joint interrogation scheme, where we
simultaneously prepare a cold-atom source and operate an atom interferometer
(AI) enables us to eliminate the dead times. We show that such continuous
operation improves the short-term sensitivity of AIs, and demonstrate a
rotation sensitivity of in a
cold-atom gyroscope of Sagnac area. We also demonstrate a
rotation stability of at s of integration time,
which establishes the record for atomic gyroscopes. The continuous operation of
cold-atom inertial sensors will enable to benefit from the full sensitivity
potential of large area AIs, determined by the quantum noise limit.Comment: 4 pages, 3 figure
Metrology with Atom Interferometry: Inertial Sensors from Laboratory to Field Applications
Developments in atom interferometry have led to atomic inertial sensors with
extremely high sensitivity. Their performances are for the moment limited by
the ground vibrations, the impact of which is exacerbated by the sequential
operation, resulting in aliasing and dead time. We discuss several experiments
performed at LNE-SYRTE in order to reduce these problems and achieve the
intrinsic limit of atomic inertial sensors. These techniques have resulted in
transportable and high-performance instruments that participate in gravity
measurements, and pave the way to applications in inertial navigation.Comment: 7 pages, 5 figure
Momentum distribution of 1D Bose gases at the quasi-condensation crossover: theoretical and experimental investigation
We investigate the momentum distribution of weakly interacting 1D Bose gases
at thermal equilibrium both experimentally and theoretically. Momentum
distribution of single 1D Bose gases is measured using a focusing technique,
whose resolution we improve via a guiding scheme. The momentum distribution
compares very well with quantum Monte Carlo calculations for the Lieb-Liniger
model at finite temperature, allowing for an accurate thermometry of the gas
that agrees with (and improves upon) the thermometry based on in situ density
fluctuation measurements. The quasi-condensation crossover is investigated via
two different experimental parameter sets, corresponding to the two different
sides of the crossover. Classical field theory is expected to correctly
describe the quasi-condensation crossover of weakly interacting gases. We
derive the condition of validity of the classical field theory, and find that,
in typical experiments, interactions are too strong for this theory to be
accurate. This is confirmed by a comparison between the classical field
predictions and the numerically exact quantum Monte Carlo calculations.Comment: 8 page
HIV-1 is budded from CD4+ T lymphocytes independently of exosomes
The convergence of HIV-1 budding and exosome biogenesis at late endosomal compartments called multivesicular bodies has fueled the debate on whether HIV-1 is budded from its target cells and transmitted in the form of exosomes. The point of contention appears to primarily derive from the types of target cells in question and lack of a well-defined protocol to separate exosomes from HIV-1. In this study, we adapted and established a simplified protocol to define the relationship between HIV-1 production and exosome biogenesis. Importantly, we took advantage of the newly established protocol to unequivocally show that HIV-1 was produced from CD4+ T lymphocytes Jurkat cells independently of exosomes. Thus, this study not only presents a simplified way to obtain highly purified HIV-1 virions for identification of host proteins packaged into virions, but also provides a technical platform that can be employed to define the relationship between exosome biogenesis and budding of HIV-1 or other viruses and its contributions to viral pathogenesis
Diastolic dysfunction in diabetes and the metabolic syndrome: promising potential for diagnosis and prognosis
Cardiac disease in diabetes mellitus and in the metabolic syndrome consists of both vascular and myocardial abnormalities. The latter are characterised predominantly by diastolic dysfunction, which has been difficult to evaluate in spite of its prevalence. While traditional Doppler echocardiographic parameters enable only semiquantitative assessment of diastolic function and cannot reliably distinguish perturbations in loading conditions from altered diastolic functions, new technologies enable detailed quantification of global and regional diastolic function. The most readily available technique for the quantification of subclinical diastolic dysfunction is tissue Doppler imaging, which has been integrated into routine contemporary clinical practice, whereas cine magnetic resonance imaging (CMR) remains a promising complementary research tool for investigating the molecular mechanisms of the disease. Diastolic function is reported to vary linearly with age in normal persons, decreasing by 0.16 cm/s each year. Diastolic function in diabetes and the metabolic syndrome is determined by cardiovascular risk factors that alter myocardial stiffness and myocardial energy availability/bioenergetics. The latter is corroborated by the improvement in diastolic function with improvement in metabolic control of diabetes by specific medical therapy or lifestyle modification. Accordingly, diastolic dysfunction reflects the structural and metabolic milieu in the myocardium, and may allow targeted therapeutic interventions to modulate cardiac metabolism to prevent heart failure in insulin resistance and diabetes
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