2,444 research outputs found
On the predictability of sea surface height around Palau
Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(11), (2020): 3267–3294, https://doi.org/10.1175/JPO-D-19-0310.1.As part of the Flow Encountering Abrupt Topography (FLEAT) program, an array of pressure-sensor equipped inverted echo sounders (PIESs) was deployed north of Palau where the westward-flowing North Equatorial Current encounters the southern end of the Kyushu–Palau Ridge in the tropical North Pacific. Capitalizing on concurrent observations from satellite altimetry, FLEAT Spray gliders, and shipboard hydrography, the PIESs’ 10-month duration hourly bottom pressure p and round-trip acoustic travel time τ records are used to examine the magnitude and predictability of sea level and pycnocline depth changes and to track signal propagations through the array. Sea level and pycnocline depth are found to vary in response to a range of ocean processes, with their magnitude and predictability strongly process dependent. Signals characterized here comprise the barotropic tides, semidiurnal and diurnal internal tides, southeastward-propagating superinertial waves, westward-propagating mesoscale eddies, and a strong signature of sea level increase and pycnocline deepening associated with the region’s relaxation from El Niño to La Niña conditions. The presence of a broad band of superinertial waves just above the inertial frequency was unexpected and the FLEAT observations and output from a numerical model suggest that these waves detected near Palau are forced by remote winds east of the Philippines. The PIES-based estimates of pycnocline displacement are found to have large uncertainties relative to overall variability in pycnocline depth, as localized deep current variations arising from interactions of the large-scale currents with the abrupt topography around Palau have significant travel time variability.Support for this research was provided by Office of Naval Research Grants N00014-16-1-2668, N00014-18-1-2406, N00014-15-1-2488, and N00014-15-1-2622. R.C.M. was additionally supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Weston Howland Jr. Postdoctoral Scholarship
Scaling near Quantum Chaos Border in Interacting Fermi Systems
The emergence of quantum chaos for interacting Fermi systems is investigated
by numerical calculation of the level spacing distribution as function
of interaction strength and the excitation energy above the
Fermi level. As increases, undergoes a transition from Poissonian
(nonchaotic) to Wigner-Dyson (chaotic) statistics and the transition is
described by a single scaling parameter given by , where is a constant. While the exponent ,
which determines the global change of the chaos border, is indecisive within a
broad range of , finite value of , which comes from the
increase of the Fock space size with , suggests that the transition
becomes sharp as increases.Comment: 4 pages, 4 figures, to appear in Phys. Rev. E (Rapid Communication
Pairing in the quantum Hall system
We find an analogy between the single skyrmion state in the quantum Hall
system and the BCS superconducting state and address that the quantum
mechanical origin of the skyrmion is electronic pairing. The skyrmion phase is
found to be unstable for magnetic fields above the critical field at
temperature , which is well represented by the relation .Comment: revtex, two figures, to appear in Phys. Rev. B (Rapid Communications
Correlation effects in a quantum dot at high magnetic fields
We investigate the effects of electron correlations on the ground state
energy and the chemical potential of a droplet confined by a parabolic
potential at high magnetic fields. We demonstrate the importance of
correlations in estimating the transition field at which the first edge
reconstruction of the maximum density droplet occurs in the spin polarized
regime.Comment: 11 pages (revtex) 3 postscript figures are included at the end of the
tex file. To appear in Phys. Rev.
Quantum computing of quantum chaos and imperfection effects
We study numerically the imperfection effects in the quantum computing of the
kicked rotator model in the regime of quantum chaos. It is shown that there are
two types of physical characteristics: for one of them the quantum computation
errors grow exponentially with the number of qubits in the computer while for
the other the growth is polynomial. Certain similarity between classical and
quantum computing errors is also discussed.Comment: revtex, 4 pages, 4 figure
Symmetry-breaking skyrmion states in fractional quantum Hall systems
We calculate in an analyical fashion the energies and net spins of skyrmions
in fractional quantum Hall systems, based on the suggestion that skyrmion
states are spontaneously and symmetry-breaking states. The
quasihole-skyrmion state with a charge around = 1/3, where the
ground state is known as a spin-polarized ferromagnetic state, is found to
exist even in high magnetic fields up to about 7 T for GaAs samples.Comment: There is conceptual change. To appear in Phys. Rev.
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Carbonyl sulfide and carbon disulfide: Large-scale distributions over the western Pacific and emissions from Asia during TRACE-P
An extensive set of carbonyl sulfide (OCS) and carbon disulfide (CS2) observations were made as part of the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) project, which took place in the early spring 2001. TRACE-P sampling focused on the western Pacific region but in total included the geographic region 110°E to 290°E longitude, 5°N to 50°N latitude, and 0–12 km altitude. Substantial OCS and CS2 enhancements were observed for a great many air masses of Chinese and Japanese origin during TRACE-P. Over the western Pacific, mean mixing ratios of long-lived OCS and shorter-lived CS2 showed a gradual decrease by about 10% and a factor of 5–10, respectively, from the surface to 8–10 km altitude, presumably because land-based sources dominated their distribution during February through April 2001. The highest mean OCS and CS2levels (580 and 20 pptv, respectively, based on 2.5° × 2.5° latitude bins) were observed below 2 km near the coast of Asia, at latitudes between 25°N and 35°N, where urban Asian outflow was strongest. Ratios of OCS versus CO for continental SE Asia were much lower compared to Chinese and Japanese signatures and were strongly associated with biomass burning/biofuel emissions. We present a new inventory of anthropogenic Asian emissions (including biomass burning) for OCS and CS2 and compare it to emission estimates based on regional relationships of OCS and CS2 to CO and CO2. The OCS and CS2 results for the two methods compare well for continental SE Asia and Japan plus Korea and also for Chinese CS2 emissions. However, it appears that the inventory underestimates Chinese emissions of OCS by about 30–100%. This difference may be related to the fact that we did not include natural sources such as wetland emissions in our inventory, although the contributions from such sources are believed to be at a seasonal low during the study period. Uncertainties in OCS emissions from Chinese coal burning, which are poorly characterized, likely contribute to the discrepancy
Low energy transition in spectral statistics of 2D interactingfermions
We study the level spacing statistics and eigenstate properties of
spinless fermions with Coulomb interaction on a two dimensional lattice at
constant filling factor and various disorder strength. In the limit of large
lattice size, undergoes a transition from the Poisson to the
Wigner-Dyson distribution at a critical total energy independent of the number
of fermions. This implies the emergence of quantum ergodicity induced by
interaction and delocalization in the Hilbert space at zero temperature.Comment: revtex, 5 pages, 4 figures; new data for eigenfunctions are adde
Spin relaxation of conduction electrons in bulk III-V semiconductors
Spin relaxation time of conduction electrons through the Elliot-Yafet,
D'yakonov-Perel and Bir-Aronov-Pikus mechanisms is calculated theoretically for
bulk GaAs, GaSb, InAs and InSb of both - and -type. Relative importance
of each spin relaxation mechanism is compared and the diagrams showing the
dominant mechanism are constructed as a function of temperature and impurity
concentrations. Our approach is based upon theoretical calculation of the
momentum relaxation rate and allows understanding of the interplay between
various factors affecting the spin relaxation over a broad range of temperature
and impurity concentration.Comment: an error in earlier version correcte
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