639 research outputs found
On Aharonov-Casher bound states
In this work bound states for the Aharonov-Casher problem are considered.
According to Hagen's work on the exact equivalence between spin-1/2
Aharonov-Bohm and Aharonov-Casher effects, is known that the
term cannot be neglected in the
Hamiltonian if the spin of particle is considered. This term leads to the
existence of a singular potential at the origin. By modeling the problem by
boundary conditions at the origin which arises by the self-adjoint extension of
the Hamiltonian, we derive for the first time an expression for the bound state
energy of the Aharonov-Casher problem. As an application, we consider the
Aharonov-Casher plus a two-dimensional harmonic oscillator. We derive the
expression for the harmonic oscillator energies and compare it with the
expression obtained in the case without singularity. At the end, an approach
for determination of the self-adjoint extension parameter is given. In our
approach, the parameter is obtained essentially in terms of physics of the
problem.Comment: 11 pages, matches published versio
Relativistic Landau-Aharonov-Casher quantization based on the Lorentz symmetry violation background
Based on the discussions about the Aharonov-Casher effect in the Lorentz
symmetry violation background, we show that the analogue of the relativistic
Landau quantization in the Aharonov-Casher setup can be achieved in the
Lorentz-symmetry violation background.Comment: 11 pages. published in Journal of Mathematical Physic
Magnetic ground state and magnon-phonon interaction in multiferroic h-YMnO
Inelastic neutron scattering has been used to study the magneto-elastic
excitations in the multiferroic manganite hexagonal YMnO. An avoided
crossing is found between magnon and phonon modes close to the Brillouin zone
boundary in the -plane. Neutron polarization analysis reveals that this
mode has mixed magnon-phonon character. An external magnetic field along the
-axis is observed to cause a linear field-induced splitting of one of the
spin wave branches. A theoretical description is performed, using a Heisenberg
model of localized spins, acoustic phonon modes and a magneto-elastic coupling
via the single-ion magnetostriction. The model quantitatively reproduces the
dispersion and intensities of all modes in the full Brillouin zone, describes
the observed magnon-phonon hybridized modes, and quantifies the magneto-elastic
coupling. The combined information, including the field-induced magnon
splitting, allows us to exclude several of the earlier proposed models and
point to the correct magnetic ground state symmetry, and provides an effective
dynamic model relevant for the multiferroic hexagonal manganites.Comment: 12 pages, 10 figure
Torsion pairs and rigid objects in tubes
We classify the torsion pairs in a tube category and show that they are in
bijection with maximal rigid objects in the extension of the tube category
containing the Pruefer and adic modules. We show that the annulus geometric
model for the tube category can be extended to the larger category and
interpret torsion pairs, maximal rigid objects and the bijection between them
geometrically. We also give a similar geometric description in the case of the
linear orientation of a Dynkin quiver of type A.Comment: 25 pages, 13 figures. Paper shortened. Minor errors correcte
Quantitative CT: Associations between Emphysema, Airway Wall Thickness and Body Composition in COPD
The objective of the present study was to determine the association between CT phenotypes—emphysema by low attenuation area and bronchitis by airway wall thickness—and body composition parameters in a large cohort of subjects with and without COPD. In 452 COPD subjects and 459 subjects without COPD, CT scans were performed to determine emphysema (%LAA), airway wall thickness (AWT-Pi10), and lung mass. Muscle wasting based on FFMI was assessed by bioelectrical impedance. In both the men and women with COPD, FFMI was negatively associated with %LAA. FMI was positively associated with AWT-Pi10 in both subjects with and without COPD. Among the subjects with muscle wasting, the percentage emphysema was high, but the predictive value was moderate. In conclusion, the present study strengthens the hypothesis that the subgroup of COPD cases with muscle wasting have emphysema. Airway wall thickness is positively associated with fat mass index in both subjects with and without COPD
Morphology of two dimensional fracture surface
We consider the morphology of two dimensional cracks observed in experimental
results obtained from paper samples and compare these results with the
numerical simulations of the random fuse model (RFM). We demonstrate that the
data obey multiscaling at small scales but cross over to self-affine scaling at
larger scales. Next, we show that the roughness exponent of the random fuse
model is recovered by a simpler model that produces a connected crack, while a
directed crack yields a different result, close to a random walk. We discuss
the multiscaling behavior of all these models.Comment: slightly revise
Variação fenotípica das características biométricas da semente de 20 progênies de faveleira [Cnidosculus phylluacanthus (M.Arg) Pox et K. Horffm.].
A situação sócio-econômica da região semi-árida e a restrita utilização do potencial da Caatinga podem ser explicadas, em parte, pela escassez de pesquisas mais avançadas a respeito do potencial das espécies desta vegetação. Muitos produtos florestais provenientes da vegetação do semi-árido poderiam ser explorados, trazendo benefícios diretos e indiretos para a sua população, melhorando a qualidade de vida das pessoas que nela vivem. Dentre as espécies ocorTentes na Caatinga nordestim sobressai-se a faveleira |Ciiidosculus pl.yllacaníl.us (M.Arg) Pox et K. Horffm.], utilizada extensivamente na alimentação animal. A folha madura e a casca servem de forragem aos caprinos, ovinos, asininos e bovinos. Suas sementes podem ser utilizadas na avicultura e suinocultura (VIANA & CARNEIRO,1991). Na dieta humana, a espécie apresenta-se como uma alternativa para a produção de óleo comestível e de farinha, esta rica em sais minerais e, principalmente, em protei'nas (LIMA 1989 e QUEIROGA NETO cÍ fl/. 1994). DUQUE (1980) salienta que as sementes da favela amadurecem em época diferente da da oiticica e do capulho do algodão, podendo a indústria de óleos operar mais dias por ano, e fornecer óleo comestível melhor que o de algodão e oiticica; e farinha alimentícia de alta qualidade e paladar
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