1,325 research outputs found
Dynamics and thermodynamics in spinor quantum gases
We discuss magnetism in spinor quantum gases theoretically and experimentally
with emphasis on temporal dynamics of the spinor order parameter in the
presence of an external magnetic field. In a simple coupled Gross-Pitaevskii
picture we observe a dramatic suppression of spin dynamics due to quadratic
Zeeman ''dephasing''. In view of an inhomogeneous density profile of the
trapped condensate we present evidence of spatial variations of spin dynamics.
In addition we study spinor quantum gases as a model system for thermodynamics
of Bose-Einstein condensation. As a particular example we present measurements
on condensate magnetisation due to the interaction with a thermal bath.Comment: 8 pages, 7 figure
State and Economic Segmentation: Analysis of Effects of Export- Promotion Strategy on Wage Differentials in Koreas Manufacturing Industries
The purpose of this paper is to analyze the effects of economic differentiation on worker earnings in Korea, We argue that the export-promotion policies of the state have substantially reduced segmentation of labor markets. The export promotion strategy functions to counteract industry and size effects on worker earnings and flattens wage differentials between the core and the periphery economic sectors. This result reflects the state's objective of removing the impact of institutional non-market forces on the process of earnings determination and preserving the market-pricing mechanism in labor markets. This does not mean that all forms of segmentation have been eliminated. The export promotion policy has led to a new structural inequality based on the division of the economy into a sector oriented toward production for export and a sector oriented toward production for domestic
consumption. This is an inevitable outcome of an export-promotion policy designed to maximize labor productivity
On-site and laboratory evaluations of soundscape quality in recreational urban spaces
Context: Regulations for quiet urban areas are typically based on sound level limits alone. However, the nonacoustic context may be crucial for subjective soundscape quality. Aims: This study aimed at comparing the role of sound level and nonacoustic context for subjective urban soundscape assessment in the presence of the full on-site context, the visual context only, and without context. Materials and Methods: Soundscape quality was evaluated for three recreational urban spaces by using four subjective attributes: loudness, acceptance, stressfulness, and comfort. The sound level was measured at each site and simultaneous sound recordings were obtained. Participants answered questionnaires either on site or during laboratory listening tests, in which the sound recordings were presented with or without each site’s visual context consisting of two pictures. They rated the four subjective attributes along with their preference toward eight sound sources. Results: The sound level was found to be a good predictor of all subjective parameters in the laboratory, but not on site. Although all attributes were significantly correlated in the laboratory setting, they did not necessarily covary on site. Moreover, the availability of the visual context in the listening experiment had no significant effect on the ratings. The participants were overall more positive toward natural sound sources on site. Conclusion: The full immersion in the on-site nonacoustic context may be important when evaluating overall soundscape quality in urban recreational areas. Laboratory evaluations may not fully reflect how subjective loudness, acceptance, stressfulness, and comfort are affected by sound level
Resonant and Non-Resonant Modulated Amplitude Waves for Binary Bose-Einstein Condensates in Optical Lattices
We consider a system of two Gross-Pitaevskii (GP) equations, in the presence
of an optical-lattice (OL) potential, coupled by both nonlinear and linear
terms. This system describes a Bose-Einstein condensate (BEC) composed of two
different spin states of the same atomic species, which interact linearly
through a resonant electromagnetic field. In the absence of the OL, we find
plane-wave solutions and examine their stability. In the presence of the OL, we
derive a system of amplitude equations for spatially modulated states which are
coupled to the periodic potential through the lowest-order subharmonic
resonance. We determine this averaged system's equilibria, which represent
spatially periodic solutions, and subsequently examine the stability of the
corresponding solutions with direct simulations of the coupled GP equations. We
find that symmetric (equal-amplitude) and asymmetric (unequal-amplitude)
dual-mode resonant states are, respectively, stable and unstable. The unstable
states generate periodic oscillations between the two condensate components,
which is possible only because of the linear coupling between them. We also
find four-mode states, but they are always unstable. Finally, we briefly
consider ternary (three-component) condensates.Comment: 16 pages, 4 figures (some of which have multiple parts), to appear in
Physica D; streamlined paper; added some references and discussion concerning
experimental realizations of this work; higher-resolution copies of a couple
figures are available on the version of the document downloadable from
http://www.math.gatech.edu/~mason
Dynamically turning off interactions in a two component condensate
We propose a mechanism to change the interaction strengths of a two component
condensate. It is shown that the application of pi/2 pulses allows to alter the
effective interspecies interaction strength as well as the effective
interaction strength between particles of the same kind. This mechanism
provides a simple method to transform spatially stable condensates into
unstable once and vice versa. It also provides a means to store a squeezed spin
state by turning off the interaction for the internal states and thus allows to
gain control over many body entangled states.Comment: 7 pages 5 figures, symbols changed, minor changes, to appear in Phys.
Rev.
Spin squeezing and entanglement in spinor-1 condensates
We analyze quantum correlation properties of a spinor-1 (f=1) Bose Einstein
condensate using the Gell-Mann realization of SU(3) symmetry. We show that
previously discussed phenomena of condensate fragmentation and spin-mixing can
be explained in terms of the hypercharge symmetry. The ground state of a
spinor-1 condensate is found to be fragmented for ferromagnetic interactions.
The notion of two bosonic mode squeezing is generalized to the two spin (U-V)
squeezing within the SU(3) formalism. Spin squeezing in the isospin subspace
(T) is found and numerically investigated. We also provide new results for the
stationary states of spinor-1 condensates.Comment: 9 pages, 6 figure
Trapped two-component Fermi gases with up to six particles: Energetics, structural properties, and molecular condensate fraction
We investigate small equal-mass two-component Fermi gases under external
spherically symmetric confinement in which atoms with opposite spins interact
through a short-range two-body model potential. We employ a non-perturbative
microscopic framework, the stochastic variational approach, and determine the
system properties as functions of the interspecies s-wave scattering length a,
the orbital angular momentum L of the system, and the numbers N1 and N2 of
spin-up and spin-down atoms (with N1-N2 =0 or 1 and N < 7, where N=N1+N2). At
unitarity, we determine the energies of the five- and six-particle systems for
various ranges r0 of the underlying two-body model potential and extrapolate to
the zero-range limit. These energies serve as benchmark results that can be
used to validate and assess other numerical approaches. We also present
structural properties such as the pair distribution function and the radial
density. Furthermore, we analyze the one-body and two-body density matrices. A
measure for the molecular condensate fraction is proposed and applied. Our
calculations show explicitly that the natural orbitals and the momentum
distributions of atomic Fermi gases approach those characteristic for a
molecular Bose gas if the s-wave scattering length a, a>0, is sufficiently
small.Comment: 21 pages, 15 figures; accepted for publication in special issue of
CRA
New Neutrino Mass Bounds from Sloan Digital Sky Survey III Data Release 8 Photometric Luminous Galaxies
We present neutrino mass bounds using 900,000 luminous galaxies with
photometric redshifts measured from Sloan Digital Sky Survey III Data Release
Eight (SDSS DR8). The galaxies have photometric redshifts between
and , and cover 10,000 square degrees and thus probe a volume of
3Gpc, enabling tight constraints to be derived on the amount of
dark matter in the form of massive neutrinos. A new bound on the sum of
neutrino masses eV, at 95% confidence level (CL), is
obtained after combining our sample of galaxies, which we call "CMASS", with
WMAP 7 year Cosmic Microwave Background (CMB) data and the most recent
measurement of the Hubble parameter from the Hubble Space Telescope (HST). This
constraint is obtained with a conservative multipole range choice of in order to minimize non-linearities, and a free bias parameter in each
of the four redshift bins. We study the impact of assuming this linear galaxy
bias model using mock catalogs, and find that this model causes a small () bias in . For this reason, we also quote
neutrino bounds based on a conservative galaxy bias model containing
additional, shot noise-like free parameters. In this conservative case, the
bounds are significantly weakened, e.g. eV (95% confidence
level) for WMAP+HST+CMASS (). We also study the dependence
of the neutrino bound on multipole range ( vs ) and on which combination of data sets is included as a prior. The
addition of supernova and/or Baryon Acoustic Oscillation data does not
significantly improve the neutrino mass bound once the HST prior is included.
[abridged]Comment: 14 pages, 8 figures, 1 tabl
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