2,411 research outputs found
Infrared scaling solutions beyond the Landau gauge: The maximally Abelian gauge and Abelian infrared dominance
Functional equations like exact renormalization group and Dyson-Schwinger
equations have contributed to a better understanding of non-perturbative
phenomena in quantum field theories in terms of the underlying Green functions.
In Yang-Mills theory especially the Landau gauge has been used, as it is the
most accessible gauge for these methods. The growing understanding obtained in
this gauge allows to proceed to other gauges in order to obtain more
information about the relation of different realizations of the confinement
mechanism. In the maximally Abelian gauge first results are very encouraging as
a variant of Abelian infrared dominance is found: The Abelian part of the gauge
field propagator is enhanced at low momenta and thereby dominates the dynamics
in the infrared. Its role is therefore similar to that of the ghost propagator
in the Landau gauge, where one denotes the corresponding phenomenon as ghost
dominance. Also the ambiguity of two different types of solutions (decoupling
and scaling) exists in both gauges. Here we present how the two solutions are
related in the maximally Abelian gauge. The intricacy of the system of
functional equations in this gauge required the development of some new tools
and methods as, for example, the automated derivation of the equations by the
program DoFun. We also present results for linear covariant and ghost
anti-ghost symmetric gauges.Comment: 10 pages, 2 figures, Proceedings of The Many faces of QCD, Nov. 1-5
2010, Ghent, Belgiu
Lower dimensional Yang-Mills theory as a laboratory to study the infrared regime
Lattice studies of the infrared regime of gauge theories are complicated by
the required extensive limits, the performed gauge fixing and the demand for
high statistics. Using a general power counting scheme for the infrared limit
of Landau gauge SU(N) Yang-Mills theory in arbitrary dimensions we show that
the infrared behavior of Greens functions is both qualitatively and
quantitatively similar in two, three and four spacetime dimensions. Therefore,
lower dimensional lattice simulations can serve as a simplified laboratory to
analyze the presently applied approximations and to obtain first results for
higher correlation functions.Comment: 7 pages, 6 figures; talk presented at Lattice 200
Anomalous Rashba spin-orbit interaction in InAs/GaSb quantum wells
We investigate theoretically the Rashba spin-orbit interaction in InAs/GaSb
quantum wells(QWs). We find that the Rashba spin-splitting (RSS) depends
sensitively on the thickness of the InAs layer. The RSS exhibits nonlinear
behavior for narrow InAs/GaSb QWs and the oscillating feature for wide
InAs/GaSb QWs. The nonlinear and oscillating behaviors arise from the weakened
and enhanced interband coupling. The RSS also show asymmetric features respect
to the direction of the external electric field.Comment: 3 pages, 4 figures. Appl. Phys. Lett. (in press
Improved three-dimensional color-gradient lattice Boltzmann model for immiscible multiphase flows
In this paper, an improved three-dimensional color-gradient lattice Boltzmann
(LB) model is proposed for simulating immiscible multiphase flows. Compared
with the previous three-dimensional color-gradient LB models, which suffer from
the lack of Galilean invariance and considerable numerical errors in many cases
owing to the error terms in the recovered macroscopic equations, the present
model eliminates the error terms and therefore improves the numerical accuracy
and enhances the Galilean invariance. To validate the proposed model, numerical
simulation are performed. First, the test of a moving droplet in a uniform flow
field is employed to verify the Galilean invariance of the improved model.
Subsequently, numerical simulations are carried out for the layered two-phase
flow and three-dimensional Rayleigh-Taylor instability. It is shown that, using
the improved model, the numerical accuracy can be significantly improved in
comparison with the color-gradient LB model without the improvements. Finally,
the capability of the improved color-gradient LB model for simulating dynamic
multiphase flows at a relatively large density ratio is demonstrated via the
simulation of droplet impact on a solid surface.Comment: 9 Figure
Microstrip antenna array with parasitic elements
Discussed is the design of a large microstrip antenna array in terms of subarrays consisting of one fed patch and several parasitic patches. The potential advantages of this design are discussed. Theoretical radiation patterns of a subarray in the configuration of a cross are presented
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