89,923 research outputs found
B0 - B0 bar mixing, B -> J/psi K_S and B -> X_d gamma in general MSSM
We consider the gluino-mediated SUSY contributions to B0 - B0 bar mixing, B
-> J/psi K_S and B -> X_d gamma in the mass insertion approximation. We find
the LL mixing parameter can be as large as |delta_{13}^d_{LL}| < 2*10^-1, but
the LR mixing is strongly constrained by the B -> X_d gamma branching ratio and
we find |delta_{13}^d_{LR}| < 10^-2. The implications for the direct CP
asymmetry in B -> X_d gamma and the dilepton charge asymmetry (A_{ll}) are also
discussed, where substantial deviations from the standard model predictions are
possible.Comment: 14 pages, 4 figure
Splitting of Surface Plasmon Frequencies of Metal Particles in a Nematic Liquid Crystal
We calculate the effective dielectric function for a suspension of small
metallic particles immersed in a nematic liquid crystal (NLC) host. For a
random suspension of such particles in the dilute limit, we calculate the
effective dielectric tensor exactly and show that the surface plasmon
(SP)resonance of such particles splits into two resonances, polarized parallel
and perpendicular to the NLC director. At higher concentrations, we calculate
this splitting using a generalized Maxwell-Garnett approximation, which can
also be applied to a small metal particle coated with NLC. To confirm the
accuracy of the MGA for NLC-coated spheres, we also use the Discrete Dipole
Approximation. The calculated splitting is comparable to that observed in
recent experiments on NLC-coated small metal particlesComment: 11 pages, 2 figures. To be published in Appl. Phys. Let
Determination of the Joint Confidence Region of Optimal Operating Conditions in Robust Design by Bootstrap Technique
Robust design has been widely recognized as a leading method in reducing
variability and improving quality. Most of the engineering statistics
literature mainly focuses on finding "point estimates" of the optimum operating
conditions for robust design. Various procedures for calculating point
estimates of the optimum operating conditions are considered. Although this
point estimation procedure is important for continuous quality improvement, the
immediate question is "how accurate are these optimum operating conditions?"
The answer for this is to consider interval estimation for a single variable or
joint confidence regions for multiple variables.
In this paper, with the help of the bootstrap technique, we develop
procedures for obtaining joint "confidence regions" for the optimum operating
conditions. Two different procedures using Bonferroni and multivariate normal
approximation are introduced. The proposed methods are illustrated and
substantiated using a numerical example.Comment: Two tables, Three figure
Effects of Foreground Contamination on the Cosmic Microwave Background Anisotropy Measured by MAP
We study the effects of diffuse Galactic, far-infrared extragalactic source,
and radio point source emission on the cosmic microwave background (CMB)
anisotropy data anticipated from the MAP experiment. We focus on the
correlation function and genus statistics measured from mock MAP
foreground-contaminated CMB anisotropy maps generated in a spatially-flat
cosmological constant dominated cosmological model. Analyses of the simulated
MAP data at 90 GHz (0.3 deg FWHM resolution smoothed) show that foreground
effects on the correlation function are small compared with cosmic variance.
However, the Galactic emission, even just from the region with |b| > 20 deg,
significantly affects the topology of CMB anisotropy, causing a negative genus
shift non-Gaussianity signal. Given the expected level of cosmic variance, this
effect can be effectively reduced by subtracting existing Galactic foreground
emission models from the observed data. IRAS and DIRBE far-infrared
extragalactic sources have little effect on the CMB anisotropy. Radio point
sources raise the amplitude of the correlation function considerably on scales
below 0.5 deg. Removal of bright radio sources above a 5 \sigma detection limit
effectively eliminates this effect. Radio sources also result in a positive
genus curve asymmetry (significant at 2 \sigma) on 0.5 deg scales. Accurate
radio point source data is essential for an unambiguous detection of CMB
anisotropy non-Gaussianity on these scales. Non-Gaussianity of cosmological
origin can be detected from the foreground-subtracted CMB anisotropy map at the
2 \sigma level if the measured genus shift parameter |\Delta\nu| >= 0.02 (0.04)
or if the measured genus asymmetry parameter |\Delta g| >= 0.03 (0.08) on a 0.3
(1.0) deg FWHM scale.Comment: 26 pages, 7 figures, Accepted for Publication in Astrophysical
Journal (Some sentences and figures modified
Driven Pair Contact Process with Diffusion
The pair contact process with diffusion (PCPD) has been recently investigated
extensively, but its critical behavior is not yet clearly established. By
introducing biased diffusion, we show that the external driving is relevant and
the driven PCPD exhibits a mean-field-type critical behavior even in one
dimension. In systems which can be described by a single-species bosonic field
theory, the Galilean invariance guarantees that the driving is irrelevant. The
well-established directed percolation (DP) and parity conserving (PC) classes
are such examples. This leads us to conclude that the PCPD universality class
should be distinct from the DP or PC class. Moreover, it implies that the PCPD
is generically a multi-species model and a field theory of two species is
suitable for proper description
Influence of Dzyaloshinskii-Moriya interactions on magnetic structure of a spin-1/2 deformed kagome lattice antiferromagnet
Motivated by the recent neutron scattering experiment on Rb2Cu3SnF12 [Nat.
Phys. 6, 865 (2010)], we investigate the effect of Dzyaloshinskii-Moriya
interactions in a theoretical model for the magnetic structure of this
material. Considering the valence bond solid ground state, which has a 12-site
unit cell, we develop the bond operator mean-field theory. It is shown that the
Dzyaloshinskii-Moriya interactions significantly modify the triplon dispersions
around the Gamma point and cause a shift of the spin gap (the minimum triplon
gap) position from the K to Gamma point in the first Brilloin zone. The spin
gap is also evaluated in exact diagonalization studies on a 24-site cluster. We
discuss a magnetic transition induced by the Dzyaloshinskii-Moriya interactions
in the bond operator framework. Moreover, the magnetization process under
external magnetic fields is studied within the exact diagonalization and strong
coupling expansion approaches. We find that the results of all above approaches
are consistent with the experimental findings.Comment: 14 pages, 10 figures; typos corrected, and acknowledgements and
references adde
Phase transition classes in triplet and quadruplet reaction diffusion models
Phase transitions of reaction-diffusion systems with site occupation
restriction and with particle creation that requires n=3,4 parents, whereas
explicit diffusion of single particles (A) is present are investigated in low
dimensions by mean-field approximation and simulations. The mean-field
approximation of general nA -> (n+k)A, mA -> (m-l)A type of lattice models is
solved and novel kind of critical behavior is pointed out. In d=2 dimensions
the 3A -> 4A, 3A -> 2A model exhibits a continuous mean-field type of phase
transition, that implies d_c<2 upper critical dimension. For this model in d=1
extensive simulations support a mean-field type of phase transition with
logarithmic corrections unlike the Park et al.'s recent study (Phys. Rev E {\bf
66}, 025101 (2002)). On the other hand the 4A -> 5A, 4A -> 3A quadruplet model
exhibits a mean-field type of phase transition with logarithmic corrections in
d=2, while quadruplet models in 1d show robust, non-trivial transitions
suggesting d_c=2. Furthermore I show that a parity conserving model 3A -> 5A,
2A->0 in d=1 has a continuous phase transition with novel kind of exponents.
These results are in contradiction with the recently suggested implications of
a phenomenological, multiplicative noise Langevin equation approach and with
the simulations on suppressed bosonic systems by Kockelkoren and Chat\'e
(cond-mat/0208497).Comment: 8 pages, 10 figures included, Updated with new data, figures, table,
to be published in PR
Painlev\'{e} analysis of the coupled nonlinear Schr\"{o}dinger equation for polarized optical waves in an isotropic medium
Using the Painlev\'{e} analysis, we investigate the integrability properties
of a system of two coupled nonlinear Schr\"{o}dinger equations that describe
the propagation of orthogonally polarized optical waves in an isotropic medium.
Besides the well-known integrable vector nonlinear Schr\"{o}dinger equation, we
show that there exist a new set of equations passing the Painlev\'{e} test
where the self and cross phase modulational terms are of different magnitude.
We introduce the Hirota bilinearization and the B\"{a}cklund transformation to
obtain soliton solutions and prove integrability by making a change of
variables. The conditions on the third-order susceptibility tensor imposed by these new integrable equations are explained
Low-amplitude and long-period radial velocity variations in giants HD 3574, 63 Cygni, and HD 216946 (Research Note)
Aims. We study the low-amplitude and long-period variations in evolved stars
using precise radial velocity measurements. Methods. The high-resolution,
fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) was used from
September 2004 to May 2014 as part of the exoplanet search program at the
Bohyunsan Optical Astronomy Observatory (BOAO). Results. We report the
detection of low-amplitude and long-period orbital radial velocity variations
in three evolved stars, HD 3574, 63 Cyg, and HD 216946. They have periods of
1061, 982, and 1382 days and semi-amplitudes of 376, 742, and 699 m/s,
respectively.Comment: 6 pages, 7 figures, 4 tables, accepted for publisation in Astronomy &
Astrophysic
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