1,032 research outputs found
Nonadiabatic quantum pumping in mesoscopic nanostructures
We consider a nonadiabatic quantum pumping phenomena in a ballistic narrow
constriction. The pumping is induced by a potential that has both spatial and
temporal periodicity characterized by and . In the zero frequency
() limit, the transmission through narrow constriction exhibits
valley structures due to the opening up of energy gaps in the pumping region --
a consequence of the periodicity. These valley structures remain robust in
the regime of finite , while their energies of occurrence are shifted
by about . The direction of these energy shifts depend on the
directions of both the phase-velocity of the pumping potential and the
transmitting electrons. This frequency dependent feature of the valley
structures gives rise to both the asymmetry in the transmission coefficients
and the pumping current. An experimental setup is suggested for a possible
observation of our nonadiabatic quantum pumping findings.Comment: 4 pages, 2 figure
Classification and nondegeneracy of Toda system with singular sources
We consider the following Toda system \Delta u_i + \D \sum_{j = 1}^n
a_{ij}e^{u_j} = 4\pi\gamma_{i}\delta_{0} \text{in}\mathbb R^2, \int_{\mathbb
R^2}e^{u_i} dx -1\delta_0a_{ij}\gamma_i=0\forall \;1\leq i\leq n\gamma_i+\gamma_{i+1}+...+\gamma_j \notin \mathbb Z1\leq i\leq
j\leq nu_i$ is \textit{radially symmetric} w.r.t. 0.
(iii) We prove that the linearized equation at any solution is
\textit{non-degenerate}. These are fundamental results in order to understand
the bubbling behavior of the Toda system.Comment: 28 page
Saturation and Wilson Line Distributions
We introduce a Wilson line distribution function bar{W}_tau(v) to study gluon
saturation at small Feynman x_F, or large tau=ln(1/x_F). This new distribution
can be obtained from the distribution W_tau(alpha) of the Color Glass
Condensate model and the JIMWLK renormalization group equation. bar{W}_tau(v)
is physically more relevant, and mathematically simpler to deal with because of
unitarity of the Wilson line v. A JIMWLK equation is derived for bar{W}_tau(v);
its properties are studied. These properties are used to complete Mueller's
derivation of the JIMWLK equation, though for bar{W}_tau(v) and not
W_tau(alpha). They are used to derive a generalized Balitsky-Kovchegov equation
for higher multipole amplitudes. They are also used to compute the unintegrated
gluon distribution at x_F=0, yielding a completely flat spectrum in transverse
momentum squared k^2, with a known height. This is similar but not identical to
the mean field result at small k^2.Comment: One reference and two short comments added. To appear in Physical
Revies
Bound state solutions of the Dirac-Rosen-Morse potential with spin and pseudospin symmetry
The energy spectra and the corresponding two- component spinor wavefunctions
of the Dirac equation for the Rosen-Morse potential with spin and pseudospin
symmetry are obtained. The wave ( state) solutions for this
problem are obtained by using the basic concept of the supersymmetric quantum
mechanics approach and function analysis (standard approach) in the
calculations. Under the spin symmetry and pseudospin symmetry, the energy
equation and the corresponding two-component spinor wavefunctions for this
potential and other special types of this potential are obtained. Extension of
this result to state is suggested.Comment: 18 page
Supersymmetric CP Violation in in Minimal Supergravity Model
Direct CP asymmetries and the CP violating normal polarization of lepton in
inclusive decay B \to X_s l^+ l^- are investigated in minimal supergravity
model with CP violating phases. The contributions coming from exchanging
neutral Higgs bosons are included. It is shown that the direct CP violation in
branching ratio, A_{CP}^1, is of {\cal{O}}(10^{-3}) for l=e, \mu, \tau. The CP
violating normal polarization for l=\mu can reach 0.5 percent when tan\beta is
large (say, 36). For l=\tau and in the case of large \tan\beta, the direct CP
violation in backward-forward asymmetry, A_{CP}^2, can reach one percent, the
normal polarization of \tau can be as large as a few percent, and both are
sensitive to the two CP violating phases, \phi_\mu and \phi_{A_0}, and
consequently it could be possible to observe them (in particular, the normal
polarization of \tau) in the future B factories.Comment: 14 pages, latex, 5 figure
BAs and boride III-V alloys
Boron arsenide, the typically-ignored member of the III-V arsenide series
BAs-AlAs-GaAs-InAs is found to resemble silicon electronically: its Gamma
conduction band minimum is p-like (Gamma_15), not s-like (Gamma_1c), it has an
X_1c-like indirect band gap, and its bond charge is distributed almost equally
on the two atoms in the unit cell, exhibiting nearly perfect covalency. The
reasons for these are tracked down to the anomalously low atomic p orbital
energy in the boron and to the unusually strong s-s repulsion in BAs relative
to most other III-V compounds. We find unexpected valence band offsets of BAs
with respect to GaAs and AlAs. The valence band maximum (VBM) of BAs is
significantly higher than that of AlAs, despite the much smaller bond length of
BAs, and the VBM of GaAs is only slightly higher than in BAs. These effects
result from the unusually strong mixing of the cation and anion states at the
VBM. For the BAs-GaAs alloys, we find (i) a relatively small (~3.5 eV) and
composition-independent band gap bowing. This means that while addition of
small amounts of nitrogen to GaAs lowers the gap, addition of small amounts of
boron to GaAs raises the gap (ii) boron ``semi-localized'' states in the
conduction band (similar to those in GaN-GaAs alloys), and (iii) bulk mixing
enthalpies which are smaller than in GaN-GaAs alloys. The unique features of
boride III-V alloys offer new opportunities in band gap engineering.Comment: 18 pages, 14 figures, 6 tables, 61 references. Accepted for
publication in Phys. Rev. B. Scheduled to appear Oct. 15 200
First principle study of intrinsic defects in hexagonal tungsten carbide
The characteristics of intrinsic defects are important for the understanding
of self-diffusion processes, mechanical strength, brittleness, and plasticity
of tungsten carbide, which present in the divertor of fusion reactors. Here, we
use first-principles calculations to investigate the stability of point defects
and their complexes in WC. Our calculation results confirm that the formation
energies of carbon defects are much lower than that of tungsten defects. The
outward relaxations around vacancy are found. Both interstitial carbon and
interstitial tungsten atom prefer to occupy the carbon basal plane projection
of octahedral interstitial site. The results of isolated carbon defect
diffusion show that the carbon vacancy stay for a wide range of temperature
because of extremely high diffusion barriers, while carbon interstitial
migration is activated at lower temperatures for its considerable lower
activation energy. These results provide evidence for the presumption that the
800K stage is attributed by the annealing out of carbon vacancies by long-range
migration.Comment: Submitted to Journal of Nuclear Material
Entropy-Corrected New Agegraphic Dark Energy Model in Horava-Lifshitz Gravity
In this work, we have considered the entropy-corrected new agegraphic dark
energy (ECNADE) model in Horava-Lifshitz gravity in FRW universe. We have
discussed the correspondence between ECNADE and other dark energy models such
as DBI-essence,Yang-Mills dark energy, Chameleon field, Non-linear
electrodynamics field and hessence dark energy in the context of
Horava-Lifshitz gravity and reconstructed the potentials and the dynamics of
the scalar field theory which describe the ECNADE.Comment: 12 page
Updated Safety And Efficacy Data In The Phase 1 Trial Of Patients With Mantle Cell Lymphoma (Mcl) Treated With Bruton Tyrosine Kinase (Btk) Inhibitor Zanubrutinib (Bgb‐3111)
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149513/1/hon55_2630.pd
Comparison of s- and d-wave gap symmetry in nonequilibrium superconductivity
Recent application of ultrafast pump/probe optical techniques to
superconductors has renewed interest in nonequilibrium superconductivity and
the predictions that would be available for novel superconductors, such as the
high-Tc cuprates. We have reexamined two of the classical models which have
been used in the past to interpret nonequilibrium experiments with some
success: the mu* model of Owen and Scalapino and the T* model of Parker.
Predictions depend on pairing symmetry. For instance, the gap suppression due
to excess quasiparticle density n in the mu* model, varies as n^{3/2} in d-wave
as opposed to n for s-wave. Finally, we consider these models in the context of
S-I-N tunneling and optical excitation experiments. While we confirm that
recent pump/probe experiments in YBCO, as presently interpreted, are in
conflict with d-wave pairing, we refute the further claim that they agree with
s-wave.Comment: 14 pages, 11 figure
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