100,555 research outputs found
Confinement of matter fields in compact (2+1)-dimensional QED theory of high- superconductors
We study confinement of matter fields in the effective compact
(2+1)-dimensional QED theory of high- superconductors. It is shown that
the monopole configurations do not affect the propagator of gauge potential
. Based on this result, we found that: chiral symmetry breaking and
confinement take place simultaneously in the antiferromagnetic state; neither
monopole effect nor Anderson-Higgs mechanism can cause confinement in the
d-wave superconducting state.Comment: 5 pages, no figure
Automated parameters for troubled-cell indicators using outlier detection
In Vuik and Ryan (2014) we studied the use of troubled-cell indicators for discontinuity detection in nonlinear hyperbolic partial differential equations and introduced a new multiwavelet technique to detect troubled cells. We found that these methods perform well as long as a suitable, problem-dependent parameter is chosen. This parameter is used in a threshold which decides whether or not to detect an element as a troubled cell. Until now, these parameters could not be chosen automatically. The choice of the parameter has impact on the approximation: it determines the strictness of the troubled-cell indicator. An inappropriate choice of the parameter will result in detection (and limiting) of too few or too many elements. The optimal parameter is chosen such that the minimal number of troubled cells is detected and the resulting approximation is free of spurious oscillations. In this paper we will see that for each troubled-cell indicator the sudden increase or decrease of the indicator value with respect to the neighboring values is important for detection. Indication basically reduces to detecting the outliers of a vector (one dimension) or matrix (two dimensions). This is done using Tukey's boxplot approach to detect which coefficients in a vector are straying far beyond others (Tukey, 1977). We provide an algorithm that can be applied to various troubled-cell indication variables. Using this technique the problem-dependent parameter that the original indicator requires is no longer necessary as the parameter will be chosen automatically
Spontaneous excitation of an accelerated multilevel atom in dipole coupling to the derivative of a scalar field
We study the spontaneous excitation of an accelerated multilevel atom in
dipole coupling to the derivative of a massless quantum scalar field and
separately calculate the contributions of the vacuum fluctuation and radiation
reaction to the rate of change of the mean atomic energy of the atom. It is
found that, in contrast to the case where a monopole like interaction between
the atom and the field is assumed, there appear extra corrections proportional
to the acceleration squared, in addition to corrections which can be viewed as
a result of an ambient thermal bath at the Unruh temperature, as compared with
the inertial case, and the acceleration induced correction terms show
anisotropy with the contribution from longitudinal polarization being four
times that from the transverse polarization for isotropically polarized
accelerated atoms. Our results suggest that the effect of acceleration on the
rate of change of the mean atomic energy is dependent not only on the quantum
field to which the atom is coupled, but also on the type of the interaction
even if the same quantum scalar field is considered.Comment: 11 pages, no figure
Laser Mode Bifurcations Induced by -Breaking Exceptional Points
A laser consisting of two independently-pumped resonators can exhibit mode
bifurcations that evolve out of the exceptional points (EPs) of the linear
system at threshold. The EPs are non-Hermitian degeneracies occurring at the
parity/time-reversal () symmetry breaking points of the threshold
system. Above threshold, the EPs become bifurcations of the nonlinear
zero-detuned laser modes, which can be most easily observed by making the gain
saturation intensities in the two resonators substantially different. Small
pump variations can then switch abruptly between different laser behaviors,
e.g. between below-threshold and -broken single-mode operation.Comment: 4 pages, 3 figure
Quantum anti-Zeno effect without rotating wave approximation
In this paper, we systematically study the spontaneous decay phenomenon of a
two-level system under the influences of both its environment and continuous
measurements. In order to clarify some well-established conclusions about the
quantum Zeno effect (QZE) and the quantum anti-Zeno effect (QAZE), we do not
use the rotating wave approximation (RWA) in obtaining an effective
Hamiltonian. We examine various spectral distributions by making use of our
present approach in comparison with other approaches. It is found that with
respect to a bare excited state even without the RWA, the QAZE can still happen
for some cases, e.g., the interacting spectra of hydrogen. But for a physical
excited state, which is a renormalized dressed state of the atomic state, the
QAZE disappears and only the QZE remains. These discoveries inevitably show a
transition from the QZE to the QAZE as the measurement interval changes.Comment: 14 pages, 8 figure
Transport in gapped bilayer graphene: the role of potential fluctuations
We employ a dual-gated geometry to control the band gap \Delta in bilayer
graphene and study the temperature dependence of the resistance at the charge
neutrality point, RNP(T), from 220 to 1.5 K. Above 5 K, RNP(T) is dominated by
two thermally activated processes in different temperature regimes and exhibits
exp(T3/T)^{1/3} below 5 K. We develop a simple model to account for the
experimental observations, which highlights the crucial role of localized
states produced by potential fluctuations. The high temperature conduction is
attributed to thermal activation to the mobility edge. The activation energy
approaches \Delta /2 at large band gap. At intermediate and low temperatures,
the dominant conduction mechanisms are nearest neighbor hopping and
variable-range hopping through localized states. Our systematic study provides
a coherent understanding of transport in gapped bilayer graphene.Comment: to appear in Physical Review B: Rapid Com
Fiber Based Multiple-Access Optical Frequency Dissemination
We demonstrate a fiber based multiple-access optical frequency dissemination
scheme. Without using any additional laser sources, we reproduce the stable
disseminated frequency at an arbitrary point of fiber link. Relative frequency
stability of 3E10^{-16}/s and 4E10^{-18}/10^4s is obtained. A branching fiber
network for highly-precision synchronization of optical frequency is made
possible by this method and its applications are discussed.Comment: 5 pages, 3 figure
Chiral Symmetry and the Parity-Violating Yukawa Coupling
We construct the complete SU(2) parity-violating (PV)
interaction Lagrangian with one derivative, and calculate the chiral
corrections to the PV Yukawa coupling constant through in the leading order of heavy baryon expansion. We
discuss the relationship between the renormalized \hpi, the measured value of
\hpi, and the corresponding quantity calculated microscopically from the
Standard Model four-quark PV interaction.Comment: RevTex, 26 pages + 5 PS figure
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