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Anharmonic multi-phonon nonradiative transition: An ab initio calculation approach
Nonradiative carrier recombinations at deep centers in semiconductors are of great importance for both fundamental physics and device engineering. In this article, we provide a revised analysis of Huang’s original nonradiative multi-phonon (NMP) theory with ab initio calculations. First, we confirmed at the first-principles level that Huang’s concise formula gives the same results as the matrix-based formula, and that Huang’s high-temperature formula provides an analytical expression for the coupling constant in Marcus theory. Secondly, we correct for anharmonic effects by taking into account local phonon-mode variations for different charge states of a defect. The corrected capture rates for defects in GaN and SiC agree well with experiments
The thermal evolution of nuclear matter at zero temperature and definite baryon number density in chiral perturbation theory
The thermal properties of cold dense nuclear matter are investigated with
chiral perturbation theory.
The evolution curves for the baryon number density, baryon number
susceptibility, pressure and the equation of state are obtained.
The chiral condensate is calculated and our result shows that when the baryon
chemical potential goes beyond , the absolute value of the
quark condensate decreases rapidly, which indicates a tendency of chiral
restoration.Comment: 17 pages, 9 figures, revtex
Anharmonic force field and vibrational frequencies of tetrafluoromethane (CF) and tetrafluorosilane (SiF)
Accurate quartic anharmonic force fields for CF and SiF have been
calculated using the CCSD(T) method and basis sets of quality. Based on
the {\it ab initio} force field with a minor empirical adjustment, the
vibrational energy levels of these two molecules and their isotopomers are
calculated by means of high order Canonical Van Vleck Perturbation Theory(CVPT)
based on curvilinear coordinates. The calculated energies agree very well with
the experimental data. The full quadratic force field of CF is further
refined to the experimental data. The symmetrization of the Cartesian basis for
any combination bands of group molecules is discussed using the circular
promotion operator for the doubly degenerate modes, together with tabulated
vector coupling coefficients. The extraction of the spectroscopic constants
from our second order transformed Hamiltonian in curvilinear coordinates is
discussed, and compared to a similar procedure in rectilinear coordinates.Comment: (submitted to J. Chem. Phys.
A classification of 2D fermionic and bosonic topological orders
The string-net approach by Levin and Wen, and the local unitary
transformation approach by Chen, Gu, and Wen, provide ways to classify
topological orders with gappable edge in 2D bosonic systems. The two approaches
reveal that the mathematical framework for 2+1D bosonic topological order with
gappable edge is closely related to unitary fusion category theory. In this
paper, we generalize these systematic descriptions of topological orders to 2D
fermion systems. We find a classification of 2+1D fermionic topological orders
with gappable edge in terms of the following set of data , that satisfy a set of non-linear
algebraic equations. The exactly soluble Hamiltonians can be constructed from
the above data on any lattices to realize the corresponding topological orders.
When , our result recovers the previous classification of 2+1D
bosonic topological orders with gappable edge.Comment: 19 page 5 figures, RevTeX
Multi-Context Attention for Human Pose Estimation
In this paper, we propose to incorporate convolutional neural networks with a
multi-context attention mechanism into an end-to-end framework for human pose
estimation. We adopt stacked hourglass networks to generate attention maps from
features at multiple resolutions with various semantics. The Conditional Random
Field (CRF) is utilized to model the correlations among neighboring regions in
the attention map. We further combine the holistic attention model, which
focuses on the global consistency of the full human body, and the body part
attention model, which focuses on the detailed description for different body
parts. Hence our model has the ability to focus on different granularity from
local salient regions to global semantic-consistent spaces. Additionally, we
design novel Hourglass Residual Units (HRUs) to increase the receptive field of
the network. These units are extensions of residual units with a side branch
incorporating filters with larger receptive fields, hence features with various
scales are learned and combined within the HRUs. The effectiveness of the
proposed multi-context attention mechanism and the hourglass residual units is
evaluated on two widely used human pose estimation benchmarks. Our approach
outperforms all existing methods on both benchmarks over all the body parts.Comment: The first two authors contribute equally to this wor
The Discrete AKNS-D Hierarchy
In this paper, we consider the discrete AKNS-D hierarchy, find the
construction of the hierarchy, prove the bilinear identity and give the
construction of the -functions of this hierarchy.Comment: 11 page
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