159,558 research outputs found
Nanogroove array on thin metallic film as planar lens with tunable focusing
Numerical results for the distributions of light transmitted through metallic
planar lenses composed of symmetric nanogroove arrays on the surfaces of a gold
film are presented and explained. Both the near- and far-field distributions of
the intensity of light transmitted are calculated by using a Green's function
formalism. Results for an optimal transverse focus based on a quadratic
variation of groove width are obtained. Meanwhile, a significant dependence of
the focal length on the wavelength of light incident from the air side through
the gold film into a dielectric substrate is found for this detector
configuration.Comment: 14 pages, 6 figure
Gr\"obner-Shirshov bases for -algebras
In this paper, we firstly establish Composition-Diamond lemma for
-algebras. We give a Gr\"{o}bner-Shirshov basis of the free -algebra
as a quotient algebra of a free -algebra, and then the normal form of
the free -algebra is obtained. We secondly establish Composition-Diamond
lemma for -algebras. As applications, we give Gr\"{o}bner-Shirshov bases of
the free dialgebra and the free product of two -algebras, and then we show
four embedding theorems of -algebras: 1) Every countably generated
-algebra can be embedded into a two-generated -algebra. 2) Every
-algebra can be embedded into a simple -algebra. 3) Every countably
generated -algebra over a countable field can be embedded into a simple
two-generated -algebra. 4) Three arbitrary -algebras , , over a
field can be embedded into a simple -algebra generated by and if
and , where is the free product of
and .Comment: 22 page
BCS-BEC Crossover in Symmetric Nuclear Matter at Finite Temperature: Pairing Fluctuation and Pseudogap
By adopting a -matrix based method within approximation for the
pair susceptibility, we studied the effects of pairing fluctuation on the
BCS-BEC crossover in symmetric nuclear matter. The pairing fluctuation induces
a pseudogap in the excitation spectrum of nucleon in both superfluid and normal
phases. The critical temperature of superfluid transition was calculated. It
differs from the BCS result remarkably when density is low. We also computed
the specific heat which shows a nearly ideal BEC type temperature dependence at
low density but a BCS type behavior at high density. This qualitative change of
the temperature dependence of specific heat may serve as a thermodynamic signal
for BCS-BEC crossover.Comment: 11 pages,11 figures,1 table, published version in Phys. Rev. C
Remote sounding through semi-transparent cirrus cloud
A large portion of the earth is covered by thin semi-transparent cirrus cloud. The cirrus results from the natural injection of moisture into the upper troposphere by deep convection (i.e., anvils) and from man-made moisture injected into the upper troposphere by jet aircraft. Although most cirrus clouds are semi-transparent to infrared wavelengths, their heights, thicknesses, and spectral absorption properties must be known in order to retrieve atmospheric temperature and moisture profiles from the data. An algorithm is developed for accounting for the radiative properties of semi-transparent cloud in the retrieval of vertical temperature and moisture profiles. The algorithm is to be applied to the NASA ER2 HIS data collected during the FIRE cirrus field program
Thermal effects on nuclear symmetry energy with a momentum-dependent effective interaction
The knowledge of the nuclear symmetry energy of hot neutron-rich matter is
important for understanding the dynamical evolution of massive stars and the
supernova explosion mechanisms. In particular, the electron capture rate on
nuclei and/or free protons in presupernova explosions is especially sensitive
to the symmetry energy at finite temperature. In view of the above, in the
present work we calculate the symmetry energy as a function of the temperature
for various values of the baryon density, by applying a momentum-dependent
effective interaction. In addition to a previous work, the thermal effects are
studied separately both in the kinetic part and the interaction part of the
symmetry energy. We focus also on the calculations of the mean field potential,
employed extensively in heavy ion reaction research, both for nuclear and pure
neutron matter. The proton fraction and the electron chemical potential, which
are crucial quantities for representing the thermal evolution of supernova and
neutron stars, are calculated for various values of the temperature. Finally,
we construct a temperature dependent equation of state of -stable
nuclear matter, the basic ingredient for the evaluation of the neutron star
properties.Comment: 18 pages, 10 figures, 1 table, accepted for publication in Physical
Review
Spontaneous current generation in the gapless 2SC phase
It is found that, except chromomagnetic instability, the gapless 2SC phase
also exhibits a paramagnetic response to the perturbation of an external color
neutral baryon current. The spontaneously generated baryon current driven by
the mismatch is equivalent to the one-plane wave LOFF state. We describe the
2SC phase in the nonlinear realization framework, and show that each
instability indicates the spontaneous generation of the corresponding pseudo
Nambu-Golstone current. We show this Nambu-Goldstone currents generation state
covers the gluon phase as well as the one-plane wave LOFF state. We further
point out that, when charge neutrality condition is required, there exists a
narrow unstable LOFF (Us-LOFF) window, where not only off-diagonal gluons but
the diagonal 8-th gluon cannot avoid the magnetic instability. We discuss that
the diagonal magnetic instability in this Us-LOFF window cannot be cured by
off-diagonal gluon condensate in color superconducting phase, and it will also
show up in some constrained Abelian asymmetric superfluid/superconducting
system.Comment: 8 pages, no figure, final version to appear in PR
Competition between symmetry breaking and onset of collapse in weakly coupled atomic condensates
We analyze the symmetry breaking of matter-wave solitons in a pair of
cigar-shaped traps coupled by tunneling of atoms. The model is based on a
system of linearly coupled nonpolynomial Schr\"odinger equations (NPSEs).
Unlike the well-known spontaneous-symmetry-breaking (SSB) bifurcation in
coupled cubic equations, in the present model the SSB competes with the onset
of collapse in this system. Stability regions of symmetric and asymmetric
solitons, as well as the collapse region, are identified in the parameter space
of the system.Comment: Physical Review A, in pres
Virial Expansion of the Nuclear Equation of State
We study the equation of state (EOS) of nuclear matter as function of
density. We expand the energy per particle (E/A) of symmetric infinite nuclear
matter in powers of the density to take into account 2,3,. . .,N-body forces.
New EOS are proposed by fitting ground state properties of nuclear matter
(binding energy, compressibility and pressure) and assuming that at high
densities a second order phase transition to the Quark Gluon Plasma (QGP)
occurs. The latter phase transition is due to symmetry breaking at high density
from nuclear matter (locally color white) to the QGP (globally color white). In
the simplest implementation of a second order phase transition we calculate the
critical exponent ? by using Landau's theory of phase transition. We find ? =
3. Refining the properties of the EOS near the critical point gives ? = 5 in
agreement with experimental results. We also discuss some scenarios for the EOS
at finite temperatures
Ka-band MMIC beam steered transmitter array
A 32-GHz six-element linear transmitter array utilizing monolithic microwave integrated circuit (MMIC) phase shifters and power amplifiers was designed and tested as part of the development of a spacecraft array feed for NASA deep-space communications applications. Measurements of the performance of individual phase shifters, power amplifiers, and microstrip radiators were carried out, and electronic beam steering of the linear array was demonstrated. The switched-line phase shifters were accurate to within 7 percent on average and the power amplifier 1-dB compressed output power varied over 0.3 dB. The array had a beamwidth of 7.5 deg and demonstrated acceptable beam steering over + or - 8 deg. From the results, it can be concluded that this MMIC phased array has adequate beam-scanning capability for use in the two-dimensional array. The areas that need to be improved are the efficiency of the MMIC power amplifier and the insertion loss of the MMIC phase shifter
Exponential Convergence Towards Stationary States for the 1D Porous Medium Equation with Fractional Pressure
We analyse the asymptotic behaviour of solutions to the one dimensional
fractional version of the porous medium equation introduced by Caffarelli and
V\'azquez, where the pressure is obtained as a Riesz potential associated to
the density. We take advantage of the displacement convexity of the Riesz
potential in one dimension to show a functional inequality involving the
entropy, entropy dissipation, and the Euclidean transport distance. An argument
by approximation shows that this functional inequality is enough to deduce the
exponential convergence of solutions in self-similar variables to the unique
steady states
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