32,723 research outputs found
Finite temperature Casimir pistons for electromagnetic field with mixed boundary conditions and its classical limit
In this paper, the finite temperature Casimir force acting on a
two-dimensional Casimir piston due to electromagnetic field is computed. It was
found that if mixed boundary conditions are assumed on the piston and its
opposite wall, then the Casimir force always tends to restore the piston
towards the equilibrium position, regardless of the boundary conditions assumed
on the walls transverse to the piston. In contrary, if pure boundary conditions
are assumed on the piston and the opposite wall, then the Casimir force always
tend to pull the piston towards the closer wall and away from the equilibrium
position. The nature of the force is not affected by temperature. However, in
the high temperature regime, the magnitude of the Casimir force grows linearly
with respect to temperature. This shows that the Casimir effect has a classical
limit as has been observed in other literatures.Comment: 14 pages, 3 figures, accepted by Journal of Physics
Relativistic linear stability equations for the nonlinear Dirac equation in Bose-Einstein condensates
We present relativistic linear stability equations (RLSE) for
quasi-relativistic cold atoms in a honeycomb optical lattice. These equations
are derived from first principles and provide a method for computing
stabilities of arbitrary localized solutions of the nonlinear Dirac equation
(NLDE), a relativistic generalization of the nonlinear Schr\"odinger equation.
We present a variety of such localized solutions: skyrmions, solitons,
vortices, and half-quantum vortices, and study their stabilities via the RLSE.
When applied to a uniform background, our calculations reveal an experimentally
observable effect in the form of Cherenkov radiation. Remarkably, the Berry
phase from the bipartite structure of the honeycomb lattice induces a
boson-fermion transmutation in the quasi-particle operator statistics.Comment: 6 pages, 3 figure
Performance of a cryogenic system prototype for the XENON1T Detector
We have developed an efficient cryogenic system with heat exchange and
associated gas purification system, as a prototype for the XENON1T experiment.
The XENON1T detector will use about 3 ton of liquid xenon (LXe) at a
temperature of 175K as target and detection medium for a dark matter search. In
this paper we report results on the cryogenic system performance focusing on
the dynamics of the gas circulation-purification through a heated getter, at
flow rates above 50 Standard Liter per Minute (SLPM). A maximum flow of 114
SLPM has been achieved, and using two heat exchangers in parallel, a heat
exchange efficiency better than 96% has been measured
Lumbar Kinematics, Functional Disability and Fear Avoidance Beliefs Among Adults with Nonspecific Chronic Low Back Pain
Objectives: This study aimed to examine correlations between lumbar kinematics, functional disability and fear avoidance beliefs among adults with nonspecific chronic low back pain (LBP). Methods: This crosssectional study was conducted between March and December 2014. A total of 32 adults diagnosed with nonspecific chronic LBP were recruited from outpatients attending either an orthopaedic clinic at a university hospital or a private physiotherapy clinic in Malaysia. Lumbar kinematics were measured using sensors attached at the first lumbar (L1) and second sacral (S2) vertebrae levels. The Oswestry Disability Index (ODI) and Fear-Avoidance Beliefs Questionnaire (FABQ) were used to assess degree of functional disability and fear avoidance beliefs, respectively. Results: For maximum range of motion, positive correlations were observed between ODI scores and right lateral flexion and right rotation (P = 0.01 each), although there was a negative correlation with left rotation (P = 0.03). With maximum angular velocity, ODI scores were positively correlated with right and left lateral flexion L1 (P = 0.01 and <0.01, respectively) but negatively correlated with left lateral flexion L2 (P= 0.04). Regarding minimum angular velocity, ODI scores were positively correlated with left lateral flexion S2 (P <0.01) but negatively correlated with right and left lateral flexion L1 (P = 0.02 each), right rotation L1 (P = 0.02) and left rotation S2 (P = 0.01). No significant correlations were found between lumbar kinematics and FABQ scores. Conclusion: These findings suggest that certain lumbar kinematic parameters are correlated with functional disability, but not with fear avoidance beliefs
Entanglement and statistics in Hong-Ou-Mandel interferometry
Hong-Ou-Mandel interferometry allows one to detect the presence of
entanglement in two-photon input states. The same result holds for
two-particles input states which obey to Fermionic statistics. In the latter
case however anti-bouncing introduces qualitative differences in the
interferometer response. This effect is analyzed in a Gedankenexperiment where
the particles entering the interferometer are assumed to belong to a
one-parameter family of quons which continuously interpolate between the
Bosonic and Fermionic statistics.Comment: 7 pages, 3 figures; minor editorial changes and new references adde
A Case Study Of Learning In A Thai Manufacturing Organization
This study examines the relationships between individual, team and organizational learning of 1103 workers from a Thai manufacturing organization. Individual learning was conceptualized in terms of individuals’ learning strategies and motivation to learn. Team learning consisted of internal team learning and external team learning. Organizational learning was believed to be underpinned by commitment to learning, shared vision and open mindedness. These three levels of learning were inter-related. Thus, individuals who are interested in self development are more likely to contribute positively to teamwork and the benefits from the team learning could flow to the organizational level. The theoretical and practical implications are discussed. 
Finite Temperature Casimir Effect and Dispersion in the Presence of Compactified Extra Dimensions
Finite temperature Casimir theory of the Dirichlet scalar field is developed,
assuming that there is a conventional Casimir setup in physical space with two
infinitely large plates separated by a gap R and in addition an arbitrary
number q of extra compacified dimensions. As a generalization of earlier
theory, we assume in the first part of the paper that there is a scalar
'refractive index' N filling the whole of the physical space region. After
presenting general expressions for free energy and Casimir forces we focus on
the low temperature case, as this is of main physical interest both for force
measurements and also for issues related to entropy and the Nernst theorem.
Thereafter, in the second part we analyze dispersive properties, assuming for
simplicity q=1, by taking into account dispersion associated with the first
Matsubara frequency only. The medium-induced contribution to the free energy,
and pressure, is calculated at low temperatures.Comment: 25 pages, one figure. Minor changes in the discussion. Version to
appear in Physica Script
Surface-reconstructed Icosahedral Structures for Lead Clusters
We describe a new family of icosahedral structures for lead clusters. In
general, structures in this family contain a Mackay icosahedral core with a
reconstructed two-shell outer-layer. This family includes the anti-Mackay
icosahedra, which have have a Mackay icosahedral core but with most of the
surface atoms in hexagonal close-packed positions. Using a many-body glue
potential for lead, we identify two icosahedral structures in this family which
have the lowest energies of any known structure in the size range from 900 to
15000 lead atoms. We show that these structures are stabilized by a feature of
the many-body glue part of the interatomic potential.Comment: 9 pages, 8 figure
New Measurement of the Relative Scintillation Efficiency of Xenon Nuclear Recoils Below 10 keV
Liquid xenon is an important detection medium in direct dark matter
experiments, which search for low-energy nuclear recoils produced by the
elastic scattering of WIMPs with quarks. The two existing measurements of the
relative scintillation efficiency of nuclear recoils below 20 keV lead to
inconsistent extrapolations at lower energies. This results in a different
energy scale and thus sensitivity reach of liquid xenon dark matter detectors.
We report a new measurement of the relative scintillation efficiency below 10
keV performed with a liquid xenon scintillation detector, optimized for maximum
light collection. Greater than 95% of the interior surface of this detector was
instrumented with photomultiplier tubes, giving a scintillation yield of 19.6
photoelectrons/keV electron equivalent for 122 keV gamma rays. We find that the
relative scintillation efficiency for nuclear recoils of 5 keV is 0.14, staying
constant around this value up to 10 keV. For higher energy recoils we measure a
value around 20%, consistent with previously reported data. In light of this
new measurement, the XENON10 experiment's results on spin-independent
WIMP-nucleon cross section, which were calculated assuming a constant 0.19
relative scintillation efficiency, change from cm to
cm for WIMPs of mass 100 GeV/c, and from
cm to cm for WIMPs of mass 30
GeV/c.Comment: 8 pages, 8 figure
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