122,912 research outputs found
Giant Shapiro Resonances in a Flux Driven Josephson Junction Necklace
We present a detailed study of the dynamic response of a ring of equally
spaced Josephson junctions to a time-periodic external flux, including
screening current effects. The dynamics are described by the resistively
shunted Josephson junction model, appropriate for proximity effect junctions,
and we include Faraday's law for the flux. We find that the time-averaged
characteristics show novel {\em subharmonic giant Shapiro voltage resonances},
which strongly depend on having phase slips or not, on , on the inductance
and on the external drive frequency. We include an estimate of the possible
experimental parameters needed to observe these quantized voltage spikes.Comment: 8 pages RevTeX, 3 figures available upon reques
Light Gravitinos at Colliders and Implications for Cosmology
Light gravitinos, with mass in the eV to MeV range, are well-motivated in
particle physics, but their status as dark-matter candidates is muddled by
early-Universe uncertainties. We investigate how upcoming data from colliders
may clarify this picture. Light gravitinos are produced primarily in the decays
of the next-to-lightest supersymmetric particle, resulting in spectacular
signals, including di-photons, delayed and non-pointing photons, kinked charged
tracks, and heavy metastable charged particles. We find that the Tevatron with
20/fb and the 7 TeV LHC with 1/fb may both see evidence for hundreds of
light-gravitino events. Remarkably, this collider data is also well suited to
distinguish between currently viable light-gravitino scenarios, with striking
implications for structure formation, inflation, and other early-Universe
cosmology.Comment: 12 pages, 6 figures. To be submitted to Phys. Rev. D
Absolute rate of the reaction of hydrogen atoms with ozone from 219-360 K
Absolute rate constants for the reaction of atomic hydrogen with ozone were obtained over the temperature range 219-360 K by the flash photolysis-resonance fluorescence technique. The results can be expressed in Arrhenius form by K = (1.33 plus or minus 0.32)x10 to the minus 10 power exp (-449 plus or minus 58/T) cu cm/molecule/s (two standard deviations). The present work is compared to two previous determinations and is discussed theoretically
Absolute rate of the reaction of bromine atoms with ozone from 200-360 K
The rate constant for the reaction Br + O3 yields BrO + O2 was measured from 200 to 360 K by the technique of flash photolysis coupled to time resolved detection of bromine atoms by resonance fluorescence (FP-RF). Br atoms were produced by the flash photolysis of CH3Br at lambda 165nm.O3 was monitored continuously under reaction conditions by absorption at 253.7 nm. At each of five temperatures the results were independent of substantial variations in O3, total pressure and limited variations in flash intensity. The measured rate constants obeyed the Arrhenius expression, where the error quoted is two standard deviations. Results are compared with previous determinations which employed the discharge flow-mass spectrometric technique
Negative oxygen vacancies in HfO as charge traps in high-k stacks
We calculated the optical excitation and thermal ionization energies of
oxygen vacancies in m-HfO using atomic basis sets, a non-local density
functional and periodic supercell. The thermal ionization energies of
negatively charged V and V centres are consistent with values
obtained by the electrical measurements. The results suggest that negative
oxygen vacancies are the likely candidates for intrinsic electron traps in the
hafnum-based gate stack devices.Comment: 3 pages, 2 figure
Diagnosing numerical Cherenkov instabilities in relativistic plasma simulations based on general meshes
Numerical Cherenkov radiation (NCR) or instability is a detrimental effect
frequently found in electromagnetic particle-in-cell (EM-PIC) simulations
involving relativistic plasma beams. NCR is caused by spurious coupling between
electromagnetic-field modes and multiple beam resonances. This coupling may
result from the slow down of poorly-resolved waves due to numerical (grid)
dispersion and from aliasing mechanisms. NCR has been studied in the past for
finite-difference-based EM-PIC algorithms on regular (structured) meshes with
rectangular elements. In this work, we extend the analysis of NCR to
finite-element-based EM-PIC algorithms implemented on unstructured meshes. The
influence of different mesh element shapes and mesh layouts on NCR is studied.
Analytic predictions are compared against results from finite-element-based
EM-PIC simulations of relativistic plasma beams on various mesh types.Comment: 31 pages, 20 figure
Quantum chaos algorithms and dissipative decoherence with quantum trajectories
Using the methods of quantum trajectories we investigate the effects of
dissipative decoherence in a quantum computer algorithm simulating dynamics in
various regimes of quantum chaos including dynamical localization, quantum
ergodic regime and quasi-integrable motion.
As an example we use the quantum sawtooth algorithm which can be implemented
in a polynomial number of quantum gates.
It is shown that the fidelity of quantum computation decays exponentially
with time and that the decay rate is proportional to the number of qubits,
number of quantum gates and per gate dissipation rate induced by external
decoherence.
In the limit of strong dissipation the quantum algorithm generates a quantum
attractor which may have complex or simple structure.
We also compare the effects of dissipative decoherence with the effects of
static imperfections.Comment: 6 pages, 6 figs, research at http://www.quantware.ups-tlse.f
Sigma meson in QCD sum rules using a two quark current with derivatives
We study the meson in QCD sum rules using a two quark interpolating
field with derivatives. In the constituent quark model, the meson is
composed of a quark and an antiquark in the relative p-wave state and is thus
expected to have a larger overlap with an interpolating field that measures the
derivative of the relative quark wave-function. While the sum rule with a
current without derivatives gives a pole mass of around 1 GeV, the present sum
rule with a derivative current gives a mass of around 550 MeV and a width of
400 MeV, that could be identified with the meson.Comment: 4 pages, 2 figure
Geothermal probabilistic cost study
A tool is presented to quantify the risks of geothermal projects, the Geothermal Probabilistic Cost Model (GPCM). The GPCM model was used to evaluate a geothermal reservoir for a binary-cycle electric plant at Heber, California. Three institutional aspects of the geothermal risk which can shift the risk among different agents was analyzed. The leasing of geothermal land, contracting between the producer and the user of the geothermal heat, and insurance against faulty performance were examined
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