42,759 research outputs found
Coronal and chromospheric physics
The Solar Maximum Mission support program is mentioned along with investigations of the solar corona, prominences, and chromosphere. The solar limb was studied using far infrared and submillimeter photometry. Stokes profiles obtained from sunspot observations were examined with a polarimetric technique
Coulomb plus power-law potentials in quantum mechanics
We study the discrete spectrum of the Hamiltonian H = -Delta + V(r) for the
Coulomb plus power-law potential V(r)=-1/r+ beta sgn(q)r^q, where beta > 0, q >
-2 and q \ne 0. We show by envelope theory that the discrete eigenvalues
E_{n\ell} of H may be approximated by the semiclassical expression
E_{n\ell}(q) \approx min_{r>0}\{1/r^2-1/(mu r)+ sgn(q) beta(nu r)^q}.
Values of mu and nu are prescribed which yield upper and lower bounds.
Accurate upper bounds are also obtained by use of a trial function of the form,
psi(r)= r^{\ell+1}e^{-(xr)^{q}}. We give detailed results for
V(r) = -1/r + beta r^q, q = 0.5, 1, 2 for n=1, \ell=0,1,2, along with
comparison eigenvalues found by direct numerical methods.Comment: 11 pages, 3 figure
Semiclassical energy formulas for power-law and log potentials in quantum mechanics
We study a single particle which obeys non-relativistic quantum mechanics in
R^N and has Hamiltonian H = -Delta + V(r), where V(r) = sgn(q)r^q. If N \geq 2,
then q > -2, and if N = 1, then q > -1. The discrete eigenvalues E_{n\ell} may
be represented exactly by the semiclassical expression E_{n\ell}(q) =
min_{r>0}\{P_{n\ell}(q)^2/r^2+ V(r)}. The case q = 0 corresponds to V(r) =
ln(r). By writing one power as a smooth transformation of another, and using
envelope theory, it has earlier been proved that the P_{n\ell}(q) functions are
monotone increasing. Recent refinements to the comparison theorem of QM in
which comparison potentials can cross over, allow us to prove for n = 1 that
Q(q)=Z(q)P(q) is monotone increasing, even though the factor Z(q)=(1+q/N)^{1/q}
is monotone decreasing. Thus P(q) cannot increase too slowly. This result
yields some sharper estimates for power-potential eigenvlaues at the bottom of
each angular-momentum subspace.Comment: 20 pages, 5 figure
Effect of inversion asymmetry on the intrinsic anomalous Hall effect in ferromagnetic (Ga,Mn)As
The relativistic nature of the electron motion underlies the intrinsic part
of the anomalous Hall effect, believed to dominate in ferromagnetic (Ga,Mn)As.
In this paper, we concentrate on the crystal band structure as an important
facet to the description of this phenomenon. Using different k.p and
tight-binding computational schemes, we capture the strong effect of the bulk
inversion asymmetry on the Berry curvature and the anomalous Hall conductivity.
At the same time, we find it not to affect other important characteristics of
(Ga,Mn)As, namely the Curie temperature and uniaxial anisotropy fields. Our
results extend the established theories of the anomalous Hall effect in
ferromagnetic semiconductors and shed new light on its puzzling nature
Thermal dissipation in quantum turbulence
The microscopic mechanism of thermal dissipation in quantum turbulence has
been numerically studied by solving the coupled system involving the
Gross-Pitaevskii equation and the Bogoliubov-de Gennes equation. At low
temperatures, the obtained dissipation does not work at scales greater than the
vortex core size. However, as the temperature increases, dissipation works at
large scales and it affects the vortex dynamics. We successfully obtained the
mutual friction coefficients of the vortex dynamics as functions of
temperature, which can be applied to the vortex dynamics in dilute
Bose-Einstein condensates.Comment: 4 pages, 6 figures, submitted to AP
Chiral extrapolation beyond the power-counting regime
Chiral effective field theory can provide valuable insight into the chiral
physics of hadrons when used in conjunction with non-perturbative schemes such
as lattice QCD. In this discourse, the attention is focused on extrapolating
the mass of the rho meson to the physical pion mass in quenched QCD (QQCD).
With the absence of a known experimental value, this serves to demonstrate the
ability of the extrapolation scheme to make predictions without prior bias. By
using extended effective field theory developed previously, an extrapolation is
performed using quenched lattice QCD data that extends outside the chiral
power-counting regime (PCR). The method involves an analysis of the
renormalization flow curves of the low energy coefficients in a finite-range
regularized effective field theory. The analysis identifies an optimal
regulator, which is embedded in the lattice QCD data themselves. This optimal
regulator is the regulator value at which the renormalization of the low energy
coefficients is approximately independent of the range of quark masses
considered. By using recent precision, quenched lattice results, the
extrapolation is tested directly by truncating the analysis to a set of points
above 380 MeV, while being blinded of the results probing deeply into the
chiral regime. The result is a successful extrapolation to the chiral regime.Comment: 8 pages, 18 figure
Mountain-Shaped Coupler for Ultra Wideband Applications
This paper demonstrates a novel mountain-shaped design for a compact 3-dB coupler operating at ultra-wideband (UWB) frequencies from 3.1GHz to 10.6 GHz. The proposed design was accomplished using multilayer technology in which the structure is formed by three layers of conductors interleaved by a layer of substrate between each conductor layer. Simulation was carried out using CST Microwave Studio; the result was then compared with results from rectangular and star-shaped couplers that implemented the same technique. The results obtained show that the proposed new coupler has better performance compared to both rectangular and star-shaped coupler designs in terms of return loss, isolation, and phase difference. The coupler was fabricated and measured; the measurement results satisfactorily agree with the simulation results
Transverse laser cooling of a thermal atomic beam of dysprosium
A thermal atomic beam of dysprosium (Dy) atoms is cooled using the
transition at 421 nm. The cooling is
done via a standing light wave orthogonal to the atomic beam. Efficient
transverse cooling to the Doppler limit is demonstrated for all observable
isotopes of dysprosium. Branching ratios to metastable states are demonstrated
to be . A scheme for enhancement of the
nonzero-nuclear-spin-isotope cooling, as well as a method for direct
identification of possible trap states, is proposed.Comment: 5 pages, 4 figures v2: 7 pages, 7 figure
Spiked oscillators: exact solution
A procedure to obtain the eigenenergies and eigenfunctions of a quantum
spiked oscillator is presented. The originality of the method lies in an
adequate use of asymptotic expansions of Wronskians of algebraic solutions of
the Schroedinger equation. The procedure is applied to three familiar examples
of spiked oscillators
Textile Diamond Dipole and Artificial Magnetic Conductor Performance under Bending, Wetness and Specific Absorption Rate Measurements
Textile diamond dipole and Artificial Magnetic Conductor (AMC) have been proposed and tested under wearable and body centric measurements. The proposed antenna and AMC sheet are entirely made of textiles for both the substrate and conducting parts, thus making it suitable for wearable communications. Directive radiation patterns with high gain are obtained with the proposed AMC sheet, hence minimizing the radiation towards the human body. In this study, wearable and body centric measurements are investigated which include bending, wetness and Specific Absorption Rate (SAR). Bending is found not to give significant effect to the antenna and AMC performance, as opposed to wetness that yields severe performance distortion. However, the original performance is retrieved once the antenna and AMC dried. Moreover, notable SAR reduction is achieved with the introduction of the AMC sheet, which is appropriate to reduce the radiation that penetrates into human flesh
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