28,715 research outputs found
Canonical Formalism for Lagrangians of Maximal Nonlocality
A canonical formalism for Lagrangians of maximal nonlocality is established.
The method is based on the familiar Legendre transformation to a new function
which can be derived from the maximally nonlocal Lagrangian. The corresponding
canonical equations are derived through the standard procedure in local theory
and appear much like those local ones, though the implication of the equations
is largely expanded.Comment: 17 pages with 1 eps figur
Pressure Dependence of Wall Relaxation in Polarized He Gaseous Cells
We have observed a linear pressure dependence of longitudinal relaxation time
() at 4.2 K and 295 K in gaseous He cells made of either bare pyrex
glass or Cs/Rb-coated pyrex due to paramagnetic sites in the cell wall. The
paramagnetic wall relaxation is previously thought to be independent of He
pressure. We develop a model to interpret the observed wall relaxation by
taking into account the diffusion process, and our model gives a good
description of the data
Broadband RCS Reduction of Microstrip Patch Antenna Using Bandstop Frequency Selective Surface
In this article, a simple and effective approach is presented to reduce the Radar Cross Section (RCS) of microstrip patch antenna in ultra broad frequency band. This approach substitutes a metallic ground plane of a conventional patch antenna with a hybrid ground consisting of bandstop Frequency Selective Surface (FSS) cells with partial metallic plane. To demonstrate the validity of the proposed approach, the influence of different ground planes on antenna’s performance is investigated. Thus, a patch antenna with miniaturized FSS cells is proposed. The results suggest that this antenna shows 3dB RCS reduction almost in the whole out-of operating band within 1-20GHz for wide incident angles when compared to conventional antenna, while its radiation characteristics are sustained simultaneously. The reasonable agreement between the measured and the simulated results verifies the efficiency of the proposed approach. Moreover, this approach doesn’t alter the lightweight, low-profile, easy conformal and easy manufacturing nature of the original antenna and can be extended to obtain low-RCS antennas with metallic planes in broadband that are quite suitable for the applications which are sensitive to the variation of frequencies
Multiple Superconducting Gaps, Anisotropic Spin Fluctuations and Spin-Orbit Coupling in Iron-Pnictides
This article reviews the NMR and NQR studies on iron-based high-temperature
superconductors by the IOP/Okayama group. It was found that the electron pairs
in the superconducting state are in the spin-singlet state with multiple
fully-opened energy gaps. The antiferromagnetic spin fluctuations in the normal
state are found to be closely correlated with the superconductivity. Also the
antiferromagnetic spin fluctuations are anisotropic in the spin space, which is
different from the case in copper oxide superconductors. This anisotropy
originates from the spin-orbit coupling and is an important reflection of the
multiple-bands nature of this new class of superconductors.Comment: 20 pages, 16 figure
Is the meson dynamically generated?
We study the problem whether the meson is generated `dynamically'. A
pedagogical analysis on the toy O(N) linear sigma model is performed and we
find that the large limit and the limit does not
commute. The sigma meson may not necessarily be described as a dynamically
generated resonance. On the contrary, the sigma meson may be more appropriately
described by considering it as an explicit degree of freedom in the effective
lagrangian.Comment: Contribution to ``Quark Confinement and Hadron Spectrum VII'', 2--7
Sept. 2006, Ponta Delgada, Acores, Portuga
On the scalar nonet in the extended Nambu Jona-Lasinio model
We discuss the lightest scalar resonances, , ,
and in the extended Nambu Jona-Lasinio model. We find
that the model parameters can be tuned, but unnaturally, to accommodate for
those scalars except the . We also discuss problems encountered in
the K Matrix unitarization approximation by using counting technique.Comment: 23 pages 3 eps figures, To appear in Nucl. Phys.
Analyses of pion-nucleon elastic scattering amplitudes up to in extended-on-mass-shell subtraction scheme
We extend the analysis of elastic pion-nucleon scattering up to
level using extended-on-mass-shell subtraction scheme within the framework of
covariant baryon chiral perturbation theory. Numerical fits to partial wave
phase shift data up to GeV are performed to pin down the free
low energy constants. A good description to the existing phase shift data is
achieved. We find a good convergence for the chiral series at ,
considerably improved with respect to the -level analyses found in
previous literature. Also, the leading order contribution from explicit
resonance and partially-included loop
contribution are included to describe phase shift data up to
GeV. As phenomenological applications, we investigate chiral correction to the
Goldberger-Treiman relation % and find that it converges rapidly,
and the correction is found to be very small: . We also
get a reasonable prediction of pion-nucleon sigma term up to
by performing fits including both the pion-nucleon partial wave phase
shift data and the lattice QCD data. We report that MeV
from the fit without , and MeV from the
fit with explicit .Comment: The final version published in Phys.Rev. D 87, 054019 (2013
Consensus analysis of multi-agent systems under switching topologies by a topology-dependent average dwell time approach
© The Institution of Engineering and Technology 2016. This study addresses the consensus problem for a class of any order multi-agent systems under switching topologies which could include kinds of unconsensusable topologies. The consensus problem, depending on structure properties and the corresponding topology, is researched with fixed structure properties under directed switching topologies. By the properties of Laplacian matrix, the consensus problem for multi-agent systems is converted into the stability problem of the corresponding switched systems with a Laplacian-like matrix. Some sufficient conditions for consensus are presented by using the dwell time approach. Finally, numerical examples and the results of computer simulation are given to verify the theoretical analysis
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