1,378,329 research outputs found
Intermediate phase of the one dimensional half-filled Hubbard-Holstein model
We present a detailed numerical study of the Hubbard-Holstein model in one
dimension at half filling, including full finite-frequency quantum phonons. At
half filling, the effects of the electron-phonon and electron-electron
interactions compete, with the Holstein phonon coupling acting as an effective
negative Hubbard onsite interaction U that promotes on-site electron pairs and
a Peierls charge-density wave state. Most previous work on this model has
assumed that only Peierls or U>0 Mott insulator phases are possible at half
filling. However, there has been speculation that a third metallic phase exists
between the Peierls and Mott phases. We present results confirming the
intermediate metallic phase, and show that the Luttinger liquid correlation
exponent K_rho>1 in this region, indicating dominant superconducting pair
correlations. We explore the full phase diagram as a function of onsite Hubbard
U, phonon coupling constant, and phonon frequency.Comment: 4 pages, 4 EPS figures. v2: typos corrected. To appear in Phys. Rev.
Let
An evaluation of the relative fire hazards of jet A and jet B for commercial flight
The relative fire hazards of Jet A and Jet B aircraft fuels are evaluated. The evaluation is based on a consideration of the presence of and/or the generation of flammable mixtures in fuel systems, the ignition characteristics, and the flame propagation rates for the two fuel types. Three distinct aircraft operating regimes where fuel type may be a factor in fire hazards are considered. These are: (1) ground handling and refueling, (2) flight, and (3) crash. The evaluation indicates that the overall fire hazards for Jet A are less than for Jet B fuel
Creation of entangled states in coupled quantum dots via adiabatic rapid passage
Quantum state preparation through external control is fundamental to
established methods in quantum information processing and in studies of
dynamics. In this respect, excitons in semiconductor quantum dots (QDs) are of
particular interest since their coupling to light allows them to be driven into
a specified state using the coherent interaction with a tuned optical field
such as an external laser pulse. We propose a protocol, based on adiabatic
rapid passage, for the creation of entangled states in an ensemble of pairwise
coupled two-level systems, such as an ensemble of QD molecules. We show by
quantitative analysis using realistic parameters for semiconductor QDs that
this method is feasible where other approaches are unavailable. Furthermore,
this scheme can be generically transferred to some other physical systems
including circuit QED, nuclear and electron spins in solid-state environments,
and photonic coupled cavities.Comment: 10 pages, 2 figures. Added reference, minor changes. Discussion,
results and conclusions unchange
Analysis of perturbation solutions of varied thrust trajectories Final report
Perturbation solution analysis of vehicle transfer from one planetary circular orbit to circular orbit around another planet using low thrust acceleratio
Comment on ``Consistency, amplitudes and probabilities in quantum theory'' by A. Caticha
A carefully written paper by A. Caticha [Phys. Rev. A57, 1572 (1998)] applies
consistency arguments to derive the quantum mechanical rules for compounding
probability amplitudes in much the same way as earlier work by the present
author [J. Math. Phys. 29, 398 (1988) and Int. J. Theor. Phys. 27, 543 (1998)].
These works are examined together to find the minimal assumptions needed to
obtain the most general results
Context sensitive formulations of antenna pattern correction and side lobe compensation for NOSS/LAMMR real time processing
Large antenna multi-channel microwave radiometer (LAMMR) software specifications were written for LAMMR ground processing. There is a need to determine more computationally-efficient antenna temperature correction methods in compensating side lobe contributions especially near continents, islands and weather fronts. One of the major conclusions was that the antenna pattern corrections (APC) processes did not accomplish the implied goals of compensating for the antenna side lobe influences on brightness temperature. A-priori knowledge of land/water locations was shown to be needed and had to be incorporated in a context sensitive APC process if the artifacts caused by land presence is to be avoided. The high temperatures in land regions can severely bias the lower ocean response
NLTT5306: The shortest Period Detached White Dwarf + Brown Dwarf Binary
We have spectroscopically confirmed a brown dwarf mass companion to the
hydrogen atmosphere white dwarf NLTT5306. The white dwarf's atmospheric
parameters were measured using Sloan Digital Sky Survey and X-Shooter
spectroscopy as T_eff=7756+/-35K and log(g)=7.68+/-0.08, giving a mass for the
primary of M_WD=0.44+/-0.04 M_sun, at a distance of 71+/-4 pc with a cooling
age of 710+/-50 Myr. The existence of the brown dwarf secondary was confirmed
through the near-infrared arm of the X-Shooter data and a spectral type of
dL4-dL7 was estimated using standard spectral indices. Combined radial velocity
measurements from the Sloan Digital Sky Survey, X-Shooter and the Hobby-Eberly
Telescope's High Resolution Spectrograph of the white dwarf gives a minimum
mass of 56+/-3 M_jup for the secondary, confirming the substellar nature. The
period of the binary was measured as 101.88+/-0.02 mins using both the radial
velocity data and i'-band variability detected with the INT. This variability
indicates 'day' side heating of the brown dwarf companion. We also observe
H{\alpha} emission in our higher resolution data in phase with the white dwarf
radial velocity, indicating this system is in a low level of accretion, most
likely via a stellar wind. This system represents the shortest period white
dwarf + brown dwarf binary and the secondary has survived a stage of common
envelope evolution, much like its longer period counterpart, WD0137-349. Both
systems likely represent bona-fide progenitors of cataclysmic variables with a
low mass white dwarf and a brown dwarf donor.Comment: 9 pages, 11 figures, accepted for publication in MNRA
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