3,526 research outputs found
Noise in strong lensing cosmography
Giant arcs in strong lensing galaxy clusters can provide a purely geometric
determination of cosmological parameters, such as the dark energy density and
equation of state. We investigate sources of noise in cosmography with giant
arcs, focusing in particular on errors induced by density fluctuations along
the line-of-sight, and errors caused by modeling uncertainties. We estimate
parameter errors in two independent ways, first by developing a Fisher matrix
formalism for strong lensing parameters, and next by directly ray-tracing
through N-body simulations using a multi-plane lensing code. We show that for
reasonable power spectra, density fluctuations from large-scale structure
produce > 100% errors in cosmological parameters derived from any single
sightline, precluding the use of individual clusters or golden lenses to derive
accurate cosmological constraints. Modeling uncertainties similarly can lead to
large errors, and we show that the use of parametrized mass models in fitting
strong lensing clusters can significantly bias the inferred cosmological
parameters. We lastly speculate on means by which these errors may be
corrected.Comment: 7 pages, submitted to Ap
Intrahepatisches Sarkom der follikulÀr-dendritischen Zellen
Zusammenfassung: Wir berichten ĂŒber ein primĂ€r intrahepatisches Sarkom der follikulĂ€r-dendritischen Zellen, das bei einer 76-jĂ€hrigen Patientin auf dem Boden eines Morbus Castleman vom hyalin-vaskulĂ€ren Typ auftrat. Wir diskutieren die klinisch-pathologischen Befunde, die Pathogenese und das differenzialdiagnostische Vorgehen bei diesem seltenen Tumorty
Double radio peak and non-thermal collimated ejecta in RS Ophiuchi following the 2006 outburst
We report Multi-Element Radio-Linked Interferometer Network, Very Large Array, One-Centimetre Radio Array, Very Long Baseline Array (VLBA), Effelsberg and Giant Metrewave Radio Telescope observations beginning 4.5 days after the discovery of RS Ophiuchi undergoing its 2006 recurrent nova outburst. Observations over the first 9 weeks are included, enabling us to follow spectral development throughout the three phases of the remnant development. We see dramatic brightening on days 4 to 7 at 6 GHz and an accompanying increase in other bands, particularly 1.46 GHz, consistent with transition from the initial âfree expansionâ phase to the adiabatic expansion phase. This is complete by day 13 when the flux density at 5 GHz is apparently declining from an unexpectedly early maximum (compared with expectations from observations of the 1985 outburst). The flux density recovered to a second peak by approximately day 40, consistent with behaviour observed in 1985. At all times the spectral index is consistent with mixed non-thermal and thermal emission. The spectral indices are consistent with a non-thermal component at lower frequencies on all dates, and the spectral index changes show that the two components are clearly variable. The estimated extent of the emission at 22 GHz on day 59 is consistent with the extended east and west features seen at 1.7 GHz with the VLBA on day 63 being entirely non-thermal. We suggest a two-component model, consisting of a decelerating shell seen in mixed thermal and non-thermal emission plus faster bipolar ejecta generating the non-thermal emission, as seen in contemporaneous VLBA observations. Our estimated ejecta mass of 4 ± 2 Ă 10â7 Mâ is consistent with a white dwarf (WD) mass of 1.4 Mâ. It may be that this ejecta mass estimate is a lower limit, in which case a lower WD mass would be consistent with the data
Phase structure and monopoles in U(1) gauge theory
We investigate the phase structure of pure compact U(1) lattice gauge theory
in 4 dimensions with the Wilson action supplemented by a monopole term. To
overcome the suppression of transitions between the phases in the simulations
we make the monopole coupling a dynamical variable. We determine the phase
diagram and find that the strength of the first order transition decreases with
increasing weight of the monopole term, the transition thus ultimately getting
of second order. After outlining the appropriate topological characterization
of networks of currents lines, we present an analysis of the occurring monopole
currents which shows that the phases are related to topological properties.Comment: 22 pages (latex), 14 figures (available upon request), BU-HEP 94-
Kualitas Produk, Harga, dan Kualitas Layanan, Pengaruhnya terhadap Kepuasan Pelanggan Kartu Prabayar Tri di Kelurahan Wawalintouan Tondano Barat
Persaingan dalam bisnis operator seluler saat ini kian meningkat seiring berkembangnya teknologi komunikasi. Hal ini menuntut Perusahaan untuk terus berinovasi dalam meningkatkan kualitas produk serta layanannya dan lebih cermat dalam menentukan harga agar Perusahan dapat bersaing dengan kompetitornya. Tujuan penelitian untuk mengetahui pengaruh kualitas produk, harga serta kualitas layanan terhadap kepuasan pelanggan kartu prabayar Tri di Kelurahan Wawalintouan Tondano Barat. Penelitian ini menggunakan metode penelitian asosiatif dengan teknik analisis regresi berganda. Sampel yang digunakan 100 responden. Hasil penelitian menunjukan kualitas produk, harga serta kualitas layanan secara simultan dan parsial berpengaruh signifikan terhadap kepuasan pelanggan kartu prabayar Tri. Manajemen PT. Hutchison 3, sebaiknya tidak cepat puas dengan pencapaian yang diperoleh, melainkan terus berinovasi agar mampu meningkatkan kualitas produk, dan layanannya sehingga Perusahaan dapat tetap bertahan mengingat persaingan dalam bidang telekomunikasi semakin ketat, juga dikarenakan semakin meningkatnya selera konsumen sebagai dampak dari perkembangan zaman yang semakin modern. . Kata kunci : kualitas produk, harga, kualitas layanan, kepuasan pelangga
Magnetic properties of Quantum Corrals from first principles calculations
We present calculations for electronic and magnetic properties of surface
states confined by a circular quantum corral built of magnetic adatoms (Fe) on
a Cu(111) surface. We show the oscillations of charge and magnetization
densities within the corral and the possibility of the appearance of
spin--polarized states. In order to classify the peaks in the calculated
density of states with orbital quantum numbers we analyzed the problem in terms
of a simple quantum mechanical circular well model. This model is also used to
estimate the behaviour of the magnetization and energy with respect to the
radius of the circular corral. The calculations are performed fully
relativistically using the embedding technique within the
Korringa-Kohn-Rostoker method.Comment: 14 pages, 9 figures, submitted to J. Phys. Cond. Matt. special issue
on 'Theory and Simulation of Nanostructures
Market Disequilibria and Their Influence on Small Retail Store Pricing
In this paper a quantitative model is developed
to explain differences in average store price levels. We assume
that stores may operate under different economic regimes,
that is, under excess capacity or excess demand. Prices are
expected to be higher than average in case of an excess
demand regime and lower in an excess capacity situation.
Actual information regarding the regime that applies to each
individual store is not available. Therefore, we propose to use
a so-called 'switching model' with endogenous regime choice
to analyse the store price differences. The model developed m
the paper is estimated using four largely differing types of
stores from the Durch retail trade. These samples consist
mainly of small stores
Multicanonical Hybrid Monte Carlo: Boosting Simulations of Compact QED
We demonstrate that substantial progress can be achieved in the study of the
phase structure of 4-dimensional compact QED by a joint use of hybrid Monte
Carlo and multicanonical algorithms, through an efficient parallel
implementation. This is borne out by the observation of considerable speedup of
tunnelling between the metastable states, close to the phase transition, on the
Wilson line. We estimate that the creation of adequate samples (with order 100
flip-flops) becomes a matter of half a year's runtime at 2 Gflops sustained
performance for lattices of size up to 24^4.Comment: 15 pages, 8 figure
Macrospin approximation and quantum effects in models for magnetization reversal
The thermal activation of magnetization reversal in magnetic nanoparticles is
controlled by the anisotropy-energy barrier. Using perturbation theory, exact
diagonalization and stability analysis of the ferromagnetic spin-s Heisenberg
model with coupling or single-site anisotropy, we study the effects of quantum
fluctuations on the height of the energy barrier. Opposed to the classical
case, there is no critical anisotropy strength discriminating between reversal
via coherent rotation and via nucleation/domain-wall propagation. Quantum
fluctuations are seen to lower the barrier depending on the anisotropy
strength, dimensionality and system size and shape. In the weak-anisotropy
limit, a macrospin model is shown to emerge as the effective low-energy theory
where the microscopic spins are tightly aligned due to the ferromagnetic
exchange. The calculation provides explicit expressions for the anisotropy
parameter of the effective macrospin. We find a reduction of the
anisotropy-energy barrier as compared to the classical high spin-s limit.Comment: 10 pages, 11 figure
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