7,864 research outputs found
Active Exterior Cloaking
A new method of cloaking is presented. For two-dimensional quasistatics it is
proven how a single active exterior cloaking device can be used to shield an
object from surrounding fields, yet produce very small scattered fields. The
problem is reduced to finding a polynomial which is approximately one within
one disk and zero within a second disk, and such a polynomial is constructed.
For the two-dimensional Helmholtz equation, it is numerically shown that three
active exterior devices placed around the object suffice to produce very good
cloaking.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
DETERMINING THE EFFECTS OF LAND CHARACTERISTICS ON FARMLAND VALUES IN SOUTH-CENTRAL IDAHO
This study focused on evaluating the effects of different attributes that impact irrigated farmland values in South-central Idaho. Results indicate that study area farmland values are largely determined by agricultural productivity (profiability) related factors. However, estimated "development increment values" for parcels that seemed to be under development pressure in the study area are explainable by nonagricultural variables.Land Economics/Use,
Scanning tunneling spectroscopic studies of the pairing state of cuprate superconductors
Quasiparticle tunneling spectra of both hole-doped (p-type) and electron-doped (n-type) cuprates are studied using a low-temperature scanning tunneling microscope. The results reveal that neither the pairing symmetry nor the pseudogap phenomenon is universal among all cuprates, and that the response of n-type cuprates to quantum impurities is drastically different from that of the p-type cuprates. The only ubiquitous features among all cuprates appear to be the strong electronic correlation and the nearest-neighbor antiferromagnetic Cu2+-Cu2+ coupling in the CuO2 planes
The Calcium Triplet metallicity calibration for galactic bulge stars
We present a new calibration of the Calcium II Triplet equivalent widths
versus [Fe/H], constructed upon K giant stars in the Galactic bulge. This
calibration will be used to derive iron abundances for the targets of the GIBS
survey, and in general it is especially suited for solar and supersolar
metallicity giants, typical of external massive galaxies. About 150 bulge K
giants were observed with the GIRAFFE spectrograph at VLT, both at resolution
R~20,000 and at R~6,000. In the first case, the spectra allowed us to perform
direct determination of Fe abundances from several unblended Fe lines, deriving
what we call here high resolution [Fe/H] measurements. The low resolution
spectra allowed us to measure equivalent widths of the two strongest lines of
the near infrared Calcium II triplet at 8542 and 8662 A. By comparing the two
measurements we derived a relation between Calcium equivalent widths and [Fe/H]
that is linear over the metallicity range probed here, -1<[Fe/H]<+0.7. By
adding a small second order correction, based on literature globular cluster
data, we derived the unique calibration equation [Fe/H], with a rms dispersion of 0.197 dex, valid across the
whole metallicity range -2.3<[Fe/H]<+0.7.Comment: Accepted for publication in A&
First-Round Impacts of the 2008 Chilean Pension System Reform
Chile’s innovative privatized pension system has been lauded as possible model for Social Security system overhauls in other countries, yet it has also been critiqued for not including a strong safety net for the uncovered sector. In response, the Bachelet government in 2008 implemented reforms to rectify this shortcoming. Here we offer the first systematic effort to directly evaluate the reform’s impacts, focusing on the new Basic Solidarity Pension for poor households with at least one person age 65+. Using the Social Protection Survey, we show that targeted poor households received about 2.4 percent more household annual income, with little evidence of crowding-out of private transfers. We also suggest that recipient household welfare probably increased due to slightly higher expenditures on basic consumption including healthcare, more leisure hours, and improved self-reported health. While measured short-run effects are small, follow-ups will be essential to gauge longer-run outcomes.
Effective gravity from a quantum gauge theory in Euclidean space-time
We consider a gauge theory in an Euclidean -dimensional
space-time, which is known to be renormalizable to all orders in perturbation
theory for . Then, with the help of a space-time representation of
the gauge group, the gauge theory is mapped into a curved space-time with
linear connection. Further, in that mapping the gauge field plays the role of
the linear connection of the curved space-time and an effective metric tensor
arises naturally from the mapping. The obtained action, being quadratic in the
Riemann-Christoffel tensor, at a first sight, spoils a gravity interpretation
of the model. Thus, we provide a sketch of a mechanism that breaks the
color invariance and generates the Einstein-Hilbert term, as well as a
cosmological constant term, allowing an interpretation of the model as a
modified gravity in the Palatini formalism. In that sense, gravity can be
visualized as an effective classical theory, originated from a well defined
quantum gauge theory. We also show that, in the four dimensional case, two
possibilities for particular solutions of the field equations are the de Sitter
and Anti de Sitter space-times.Comment: 20 pages; Final version accepted for publication in Class.Quant.Gra
Dissipative Dynamics of Collisionless Nonlinear Alfven Wave Trains
The nonlinear dynamics of collisionless Alfven trains, including resonant
particle effects is studied using the kinetic nonlinear Schroedinger (KNLS)
equation model. Numerical solutions of the KNLS reveal the dynamics of Alfven
waves to be sensitive to the sense of polarization as well as the angle of
propagation with respect to the ambient magnetic field. The combined effects of
both wave nonlinearity and Landau damping result in the evolutionary formation
of stationaryOA S- and arc-polarized directional and rotational
discontinuities. These waveforms are freqently observed in the interplanetary
plasma.Comment: REVTeX, 6 pages (including 5 figures). This and other papers may be
found at http://sdphpd.ucsd.edu/~medvedev/papers.htm
Helical structures from an isotropic homopolymer model
We present Monte Carlo simulation results for square-well homopolymers at a
series of bond lengths. Although the model contains only isotropic pairwise
interactions, under appropriate conditions this system shows spontaneous chiral
symmetry breaking, where the chain exists in either a left- or a right-handed
helical structure. We investigate how this behavior depends upon the ratio
between bond length and monomer radius.Comment: 10 pages, 3 figures, accepted for publication by Physical Review
Letter
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