5,946 research outputs found
Clock spectroscopy of interacting bosons in deep optical lattices
We report on high-resolution optical spectroscopy of interacting bosonic
Yb atoms in deep optical lattices with negligible tunneling. We prepare
Mott insulator phases with singly- and doubly-occupied isolated sites and probe
the atoms using an ultra-narrow "clock" transition. Atoms in singly-occupied
sites undergo long-lived Rabi oscillations. Atoms in doubly-occupied sites are
strongly affected by interatomic interactions, and we measure their inelastic
decay rates and energy shifts. We deduce from these measurements all relevant
collisional parameters involving both clock states, in particular the intra-
and inter-state scattering lengths
Non-linear Relaxation of Interacting Bosons Coherently Driven on a Narrow Optical Transition
We study the dynamics of a two-component Bose-Einstein condensate (BEC) of
Yb atoms coherently driven on a narrow optical transition. The
excitation transfers the BEC to a superposition of states with different
internal and momentum quantum numbers. We observe a crossover with decreasing
driving strength between a regime of damped oscillations, where coherent
driving prevails, and an incoherent regime, where relaxation takes over.
Several relaxation mechanisms are involved: inelastic losses involving two
excited atoms, leading to a non-exponential decay of populations; Doppler
broadening due to the finite momentum width of the BEC and inhomogeneous
elastic interactions, both leading to dephasing and to damping of the
oscillations. We compare our observations to a two-component Gross-Pitaevskii
(GP) model that fully includes these effects. For small or moderate densities,
the damping of the oscillations is mostly due to Doppler broadening. In this
regime, we find excellent agreement between the model and the experimental
results. For higher densities, the role of interactions increases and so does
the damping rate of the oscillations. The damping in the GP model is less
pronounced than in the experiment, possibly a hint for many-body effects not
captured by the mean-field description.Comment: 7 pages, 4 figures; supplementary material available as ancillary
fil
Fast connected component labeling algorithm: a non voxel-based approach
This paper presents a new approach to achieve connected component labeling on both binary images and volumes by using the Extreme Vertices Model (EVM), a representation model for orthogonal
polyhedra, applied to digital images and volume datasets recently. In contrast with previous techniques, this method does not use a voxel-based approach but deals with the inner sections of the object.Postprint (published version
Modulación temática de las matrices de sentido en un texto narrativo: "Los años de aprendizaje de Wilhelm Meister", de Goethe
Attitudinal study of latino patients and staff members of a psychiatric intensive care unit: (Veterans Administration Hospital, Palo Alto, California)
Research Methods Tutorial
A guiding principle for conducting research in technology, science, and engineering, leading to innovation is based on our use of research methodology (both qualitative and qualitative). A brief review of research methodology will be presented with an overview of NASA process in developing aeronautics technologies and other things to consider in research including what is innovation
Magneto--thermal evolution of neutron stars
We study the mutual influence of thermal and magnetic evolution in a neutron
star's crust in axial symmetry. Taking into account realistic microphysical
inputs, we find the heat released by Joule effect consistent with the
circulation of currents in the crust, and we incorporate its effects in 2D
cooling calculations. We solve the induction equation numerically using a
hybrid method (spectral in angles, but a finite--differences scheme in the
radial direction), coupled to the thermal diffusion equation. We present the
first long term 2D simulations of the coupled magneto-thermal evolution of
neutron stars. This substantially improves previous works in which a very crude
approximation in at least one of the parts (thermal or magnetic diffusion) has
been adopted. Our results show that the feedback between Joule heating and
magnetic diffusion is strong, resulting in a faster dissipation of the stronger
fields during the first million years of a NS's life. As a consequence, all
neutron stars born with fields larger than a critical value (about 5 10^13 G)
reach similar field strengths (approximately 2-3 10^{13} G) at late times.
Irrespectively of the initial magnetic field strength, after years the
temperature becomes so low that the magnetic diffusion timescale becomes longer
than the typical ages of radio--pulsars, thus resulting in apparently no
dissipation of the field in old NS. We also confirm the strong correlation
between the magnetic field and the surface temperature of relatively young NSs
discussed in preliminary works. The effective temperature of models with strong
internal toroidal components are systematically higher than those of models
with purely poloidal fields, due to the additional energy reservoir stored in
the toroidal field that is gradually released as the field dissipates.Comment: 10 pages, 5 figures, accepted for publication in A&
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