3,141 research outputs found
Light-Cone Distribution Amplitudes for the Light Mesons
We present a study of light-cone distribution amplitudes of the light
mesons. The first few Gegenbauer moments of leading twist light-cone
distribution amplitudes are calculated by using the QCD sum rule technique.Comment: 18 pages, 9 figures, v3: a sentence revised in the introduction, to
appear in JHE
Microwave radiation induced magneto-oscillations in the longitudinal and transverse resistance of a two dimensional electron gas
We confirm the existance of magneto-resistance oscillations in a
microwave-irradiated two-dimensional electron gas, first reported in a series
of papers by Zhudov et al. and Mani et al. In our experiments, on a sample with
a more moderate mobility, the microwave induced oscillations are observed not
only in the longitudinal - but also in the transverse-resistance (Hall
resistance). The phase of the oscillations is such that the decrease (increase)
in the longitudinal resistance is accompanied by an increase (decrease) in the
absolute value of the Hall resistance. We believe that these new results
provide valuable new information to better understand the origin of this
interesting phenomenon.Comment: Accepted for publication in journal of Solid State Comunication
Stable vortex and dipole vector solitons in a saturable nonlinear medium
We study both analytically and numerically the existence, uniqueness, and
stability of vortex and dipole vector solitons in a saturable nonlinear medium
in (2+1) dimensions. We construct perturbation series expansions for the vortex
and dipole vector solitons near the bifurcation point where the vortex and
dipole components are small. We show that both solutions uniquely bifurcate
from the same bifurcation point. We also prove that both vortex and dipole
vector solitons are linearly stable in the neighborhood of the bifurcation
point. Far from the bifurcation point, the family of vortex solitons becomes
linearly unstable via oscillatory instabilities, while the family of dipole
solitons remains stable in the entire domain of existence. In addition, we show
that an unstable vortex soliton breaks up either into a rotating dipole soliton
or into two rotating fundamental solitons.Comment: To appear in Phys. Rev.
Coherent States and Modified de Broglie-Bohm Complex Quantum Trajectories
This paper examines the nature of classical correspondence in the case of
coherent states at the level of quantum trajectories. We first show that for a
harmonic oscillator, the coherent state complex quantum trajectories and the
complex classical trajectories are identical to each other. This congruence in
the complex plane, not restricted to high quantum numbers alone, illustrates
that the harmonic oscillator in a coherent state executes classical motion. The
quantum trajectories are those conceived in a modified de Broglie-Bohm scheme
and we note that identical classical and quantum trajectories for coherent
states are obtained only in the present approach. The study is extended to
Gazeau-Klauder and SUSY quantum mechanics-based coherent states of a particle
in an infinite potential well and that in a symmetric Poschl-Teller (PT)
potential by solving for the trajectories numerically. For the coherent state
of the infinite potential well, almost identical classical and quantum
trajectories are obtained whereas for the PT potential, though classical
trajectories are not regained, a periodic motion results as t --> \infty.Comment: More example
Direct Amidation of Amino Acid Derivatives Catalyzed by Arylboronic Acids: Applications in Dipeptide Synthesis
The direct amidation of amino acid derivatives catalyzed by arylboronic acids has been examined. The reaction was generally slow relative to simple amine-carboxylic acid combinations though proceeded at 65–68 °C generally avoiding racemization. 3,4,5-Trifluorophenylboronic and o-nitrophenylboronic acids were found to be the best catalysts, though for slower dipeptide formations, high catalyst loadings were required and an interesting synergistic catalytic effect between two arylboronic acids was discovered
An integrated information management model for proactive prevention of struck-by-falling-object accidents on construction sites
The construction industry is one of the most hazardous industries in many countries. Struck-by-falling-object accidents are not given adequate attention even though they are of great importance on construction sites. The objective of this paper is to analyze the proactively preventive information requirement of struck-by-falling-object accidents and propose an integrated information management model using a ZigBee RFID sensor network to fulfill these requirements. First, the frequency of particular type of objects is analyzed based on vast historical accident cases. Next, this paper analyzes the proactively preventive information requirement of struck-by-falling-object accidents and brought forth an integrated information management model. Furthermore, considering the crucial and controllable objects, an integrated information management model is proposed. This study would provide a possible approach for tracking struck-by-falling-object accidents based on real-time information for proactive prevention and could serve as a foundation for further study. © 2012 Elsevier B.V. All rights reserved
Rigorous results on superconducting ground states for attractive extended Hubbard models
We show that the exact ground state for a class of extended Hubbard models
including bond-charge, exchange, and pair-hopping terms, is the Yang
"eta-paired" state for any non-vanishing value of the pair-hopping amplitude,
at least when the on-site Coulomb interaction is attractive enough and the
remaining physical parameters satisfy a single constraint. The ground state is
thus rigorously superconducting. Our result holds on a bipartite lattice in any
dimension, at any band filling, and for arbitrary electron hopping.Comment: 12 page
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