13,477 research outputs found
Dimensional Regularization and Dimensional Reduction in the Light Cone
We calculate all the 2 to 2 scattering process in Yang-Mills theory in the
Light Cone gauge, with the dimensional regulator as the UV regulator. The IR is
regulated with a cutoff in . It supplements our earlier work, where a
Lorentz non-covariant regulator was used and the final results bear some
problems in gauge fixing. Supersymmetry relations among various amplitudes are
checked using the light cone superfields.Comment: current version accepted by PR
Nuclear Modification to Parton Distribution Functions and Parton Saturation
We introduce a generalized definition of parton distribution functions (PDFs)
for a more consistent all-order treatment of power corrections. We present a
new set of modified DGLAP evolution equations for nuclear PDFs, and show that
the resummed -type of leading nuclear size enhanced power
corrections significantly slow down the growth of gluon density at small-.
We discuss the relation between the calculated power corrections and the
saturation phenomena.Comment: 4 pages, to appear in the proceedings of QM200
Origin of intrinsic dark count in superconducting nanowire single-photon detectors
The origin of the decoherence in superconducting nanowire single-photon
detectors, the so-called dark count, was investigated. We measured the
direct-current characteristics and bias-current dependencies of the dark count
rate in a wide range of temperatures from 0.5 K to 4 K, and analyzed the
results by theoretical models of thermal fluctuations of vortices. Our results
indicate that the current-assisted unbinding of vortex-antivortex pairs is the
dominant origin of the dark count.Comment: 10 pages, 2 figure
Using Stacked Sparse Auto-Encoder and Superpixel CRF for Long-Term Visual Scene Understanding of UGVs
Multiple images have been widely used for scene understanding and navigation of unmanned ground vehicles in long term operations. However, as the amount of visual data in multiple images is huge, the cumulative error in many cases becomes untenable. This paper proposes a novel method that can extract features from a large dataset of multiple images efficiently. Then the membership K-means clustering is used for high dimensional features, and the large dataset is divided into N subdatasets to train N conditional random field (CRF) models based on superpixel. A Softmax subdataset selector is used to decide which one of the N CRF models is chosen as the prediction model for labeling images. Furthermore, some experiments are conducted to evaluate the feasibility and performance of the proposed approach
Nonlocal magnon-polaron transport in yttrium iron garnet
The spin Seebeck effect (SSE) is observed in magnetic insulator|heavy metal
bilayers as an inverse spin Hall effect voltage under a temperature gradient.
The SSE can be detected nonlocally as well, viz. in terms of the voltage in a
second metallic contact (detector) on the magnetic film, spatially separated
from the first contact that is used to apply the temperature bias (injector).
Magnon-polarons are hybridized lattice and spin waves in magnetic materials,
generated by the magnetoelastic interaction. Kikkawa et al. [Phys. Rev. Lett.
\textbf{117}, 207203 (2016)] interpreted a resonant enhancement of the local
SSE in yttrium iron garnet (YIG) as a function of the magnetic field in terms
of magnon-polaron formation. Here we report the observation of magnon-polarons
in \emph{nonlocal} magnon spin injection/detection devices for various
injector-detector spacings and sample temperatures. Unexpectedly, we find that
the magnon-polaron resonances can suppress rather than enhance the nonlocal
SSE. Using finite element modelling we explain our observations as a
competition between the SSE and spin diffusion in YIG. These results give
unprecedented insights into the magnon-phonon interaction in a key magnetic
material.Comment: 5 pages, 6 figure
Far-infrared optical properties of the pyrochlore spin ice compound Dy2Ti2O4
Near normal incident far-infrared reflectivity spectra of [111] dysprosium
titanate (Dy2Ti2O4) single crystal have been measured at different
temperatures. Seven phonon modes (eight at low temperature) are identified at
frequency below 1000 cm-1. Optical conductivity spectra are obtained by fitting
all the reflectivity spectra with the factorized form of the dielectric
function. Both the Born effective charges and the static optical primitivity
are found to increase with decreasing temperature. Moreover, phonon linewidth
narrowering and phonon modes shift with decreasing temperature are also
observed, which may result from enhanced charge localization. The redshift of
several low frequency modes is attributed to the spin-phonon coupling. All
observed optical properties can be explained within the framework of nearest
neighbor ferromagnetic(FM) spin ice model
Domain control and the enhanced electro-optical properties in relaxor single crystal PMN-PT
Jet quenching in relativistic heavy ion collisions
Parton propagation in dense nuclear matter results in elastic, inelastic and
coherent multiple soft scattering with the in-medium color charges. Such
scattering leads to calculable modifications of the hadron production cross
section that is evaluated in the framework of the perturbative QCD
factorization approach. Final state medium-induced gluon bremsstrahlung is
arguably the most efficient way of suppressing large transverse momentum
particle production in nucleus-nucleus collisions. The observed hadronic
attenuation, known as jet quenching, can be related to the properties of the
medium, such as density and temperature, and carries valuable information about
the early stages of heavy ion reactions. Non-Abelian energy loss in the
quark-gluon plasma can be studied in much greater detail through the
modification of the two particle back-to-back correlations. Perturbative
calculations give good description of the redistribution of the lost energy in
lower transverse momentum particles and predict significant increase of the
correlation width of away-side di-hadrons. In contrast, energy loss in cold
nuclear matter was found to be small but for large values of Feynman-x is
expected to complement the dynamical higher twist shadowing in experimentally
observable forward rapidity hadron suppression.Comment: Invited plenary talk at the V-th international conference on the
physics and astrophysics of the quark-gluon plasma. 8 pages, 4 figure
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