33,784 research outputs found
Simplified landscapes for optimization of shaken lattice interferometry
Motivated by recent results using shaken optical lattices to perform atom
interferometry, we explore splitting of an atom cloud trapped in a
phase-modulated ("shaken") optical lattice. Using a simple analytic model we
are able to show that we can obtain the simplest case of splitting via single-frequency shaking. This is confirmed both
via simulation and experiment. Furthermore, we are able to split with a
relative phase between the two split arms of or depending on
our shaking frequency. Addressing higher-order splitting, we determine that
splitting is sufficient to be able to accelerate the
atoms in counter-propagating lattices. Finally, we show that we can use a
genetic algorithm to optimize and splitting to within by restricting our
optimization to the resonance frequencies corresponding to single- and
two-photon transitions between Bloch bands
The Infrared and Radio Fluxes Densities of Galactic HII Regions
We derive infrared and radio flux densities of all ~1000 known Galactic HII
regions in the Galactic longitude range 17.5 < l < 65 degree. Our sample comes
from the Wide-Field Infrared Survey Explorer (WISE) catalog of Galactic \hii
regions \citep{anderson2014}. We compute flux densities at six wavelengths in
the infrared (GLIMPSE 8 microns, WISE 12 microns and 22 microns, MIPSGAL 24
microns, and Hi-GAL 70 microns and 160 microns) and two in the radio (MAGPIS 20
cm and VGPS 21 cm). All HII region infrared flux densities are strongly
correlated with their ~20 cm flux densities. All HII regions used here,
regardless of physical size or Galactocentric radius, have similar infrared to
radio flux density ratios and similar infrared colors, although the smallest
regions (pc), have slightly elevated IR to radio ratios. The colors
and , and and reliably select
HII regions, independent of size. The infrared colors of ~22 of HII
regions, spanning a large range of physical sizes, satisfy the IRAS color
criteria of \citet{wood1989} for HII regions, after adjusting the criteria to
the wavelengths used here. Since these color criteria are commonly thought to
select only ultra-compact HII regions, this result indicates that the true
ultra-compact HII region population is uncertain. Comparing with a sample of IR
color indices from star-forming galaxies, HII regions show higher
ratios. We find a weak trend of
decreasing infrared to ~20 cm flux density ratios with increasing , in
agreement with previous extragalactic results, possibly indicating a decreased
dust abundance in the outer Galaxy.Comment: 27 pages, 16 figures, 5 table
Non-unique factorization of polynomials over residue class rings of the integers
We investigate non-unique factorization of polynomials in Z_{p^n}[x] into
irreducibles. As a Noetherian ring whose zero-divisors are contained in the
Jacobson radical, Z_{p^n}[x] is atomic. We reduce the question of factoring
arbitrary non-zero polynomials into irreducibles to the problem of factoring
monic polynomials into monic irreducibles. The multiplicative monoid of monic
polynomials of Z_{p^n}[x] is a direct sum of monoids corresponding to
irreducible polynomials in Z_p[x], and we show that each of these monoids has
infinite elasticity. Moreover, for every positive integer m, there exists in
each of these monoids a product of 2 irreducibles that can also be represented
as a product of m irreducibles.Comment: 11 page
OPERA superluminal neutrinos and Kinematics in Finsler spacetime
The OPERA collaboration recently reported that muon neutrinos could be
superluminal. More recently, Cohen and Glashow pointed that such superluminal
neutrinos would be suppressed since they lose their energies rapidly via
bremsstrahlung. In this Letter, we propose that Finslerian nature of spacetime
could account for the superluminal phenomena of particles. The Finsler
spacetime permits the existence of superluminal behavior of particles while the
casuality still holds. A new dispersion relation is obtained in a class of
Finsler spacetime. It is shown that the superluminal speed is linearly
dependent on the energy per unit mass of the particle. We find that such a
superluminal speed formula is consistent with data of OPERA, MINOS and
Fermilab-1979 neutrino experiments as well as observations on neutrinos from
SN1987a.Comment: 10 pages, 2 figures. Viewpoints of Finslerian special relativity on
OPERA superluminal neutrino
Vortex State in Na_xCoO_2.yH_2O: p_x\pm ip_y-wave versus d_{x^2-y^2}\pm id_{xy}-wave Pairing
Based on an effective Hamiltonian specified in the triangular lattice with
possible - or -wave pairing, which has
close relevance to the newly discovered NaCoOHO, the
electronic structure of the vortex state is studied by solving the
Bogoliubov-de Gennes equations. It is found that -wave is favored
for the electron doping as the hopping integral . The lowest-lying vortex
bound states are found to have respectively zero and positive energies for
- and -wave superconductors, whose vortex
structures exhibit the intriguing six-fold symmetry. In the presence of strong
on-site repulsion, the antiferromagnetic and ferromagnetic orders are induced
around the vortex cores for the former and the latter, respectively, both of
which cause the splitting of the LDOS peaks due to the lifting of spin
degeneracy. STM and NMR measurements are able to probe the new features of
vortex states uncovered in this work.Comment: 4 pages, 4 figures, The slightly shorter version was submitted to PR
The momentum flux probability distribution function for ion-temperature-gradient turbulence
There has been overwhelming evidence that coherent structures play a critical role in determining the overall transport in a variety of systems. We compute the probability distribution function (PDF) tails of momentum flux and heat flux in ion-temperature-gradient turbulence, by taking into account the interaction among modons, which are assumed to be coherent structures responsible for bursty and intermittent events, contributing to the PDF tails. The tail of PDF of momentum flux R = 〈vxvy〉 is shown to be exponential with the form exp{−ξR3/2}, which is broader than a Gaussian, similar to what was found in the previous local studies. An analogous expression with the same functional dependence is found for the PDF tails of heat flux. Furthermore, we present a detailed numerical study of the dependence of the PDF tail on the temperature and density scale lengths and other physical parameters through the coefficient ξ
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