1,404 research outputs found
Spin-orbit coupling in bulk GaAs
We study the spin-orbit coupling in the whole Brillouin zone for GaAs using
both the and nearest-neighbor tight-binding
models. In the -valley, the spin splitting obtained is in good
agreement with experimental data. We then further explicitly present the
coefficients of the spin splitting in GaAs and valleys. These results
are important to the realization of spintronic device and the investigation of
spin dynamics far away from equilibrium.Comment: 8 pages, 3 figures, Physica E, in pres
W Boson Inclusive Decays to Quarkonium at the LHC
In this paper, the production rates of quarkonia eta_c, J/psi, eta_b,
Upsilon, B_c and B_c^* through W boson decay at the LHC are calculated, at the
leading order in both the QCD coupling constant and in v, the typical velocity
of the heavy quark inside of mesons. It shows that a sizable number of
quarkonia from W boson decay will be produced at the LHC. Comparison with the
predictions by using quark fragmentation mechanism is also discussed. Results
show that, for the charmonium production through W decay, the difference
between predictions by the fragmentation mechanism and complete leading order
calculation is around 3%, and it is insensitive to the uncertainties of
theoretical parameters; however, for the bottomonium and B_c^(*) productions,
the difference cannot be ignored as the fragmentation mechanism is less
applicable here due to the relatively large ratio mb/mw.Comment: Updated to match the published version in EPJ
The littlest Higgs model and Higgs boson associated production with top quark pair at high energy linear collider
In the parameter space allowed by the electroweak precision measurement data,
we consider the contributions of the new particles predicted by the littlest
Higgs() model to the Higgs boson associated production with top quark pair
in the future high energy linear collider(). We find that the
contributions mainly come from the new gauge bosons and . For
reasonable values of the free parameters, the absolute value of the relative
correction parameter can be significanly large,
which might be observed in the future experiment with .Comment: latex files, 13 pages, 3 figure
Dynamical properties of the unitary Fermi gas: collective modes and shock waves
We discuss the unitary Fermi gas made of dilute and ultracold atoms with an
infinite s-wave inter-atomic scattering length. First we introduce an efficient
Thomas-Fermi-von Weizsacker density functional which describes accurately
various static properties of the unitary Fermi gas trapped by an external
potential. Then, the sound velocity and the collective frequencies of
oscillations in a harmonic trap are derived from extended superfluid
hydrodynamic equations which are the Euler-Lagrange equations of a
Thomas-Fermi-von Weizsacker action functional. Finally, we show that this
amazing Fermi gas supports supersonic and subsonic shock waves.Comment: 9 pages, 3 figures, invited talk at the International Workshop
"Critical Stability 2011" (Erice, October 2011), to be published in the
journal Few Body System
Weak-Localization in Chaotic Versus Non-Chaotic Cavities: A Striking Difference in the Line Shape
We report experimental evidence that chaotic and non-chaotic scattering
through ballistic cavities display distinct signatures in quantum transport. In
the case of non-chaotic cavities, we observe a linear decrease in the average
resistance with magnetic field which contrasts markedly with a Lorentzian
behavior for a chaotic cavity. This difference in line-shape of the
weak-localization peak is related to the differing distribution of areas
enclosed by electron trajectories. In addition, periodic oscillations are
observed which are probably associated with the Aharonov-Bohm effect through a
periodic orbit within the cavities.Comment: 4 pages revtex + 4 figures on request; amc.hub.94.
Pre-existing virus-specific CD8+ T-cells provide protection against pneumovirus-induced disease in mice
Pneumoviruses such as pneumonia virus of mice (PVM), bovine respiratory syncytial virus (bRSV) or human (h)RSV are closely related pneumoviruses that cause severe respiratory disease in their respective hosts. It is well-known that T-cell responses are essential in pneumovirus clearance, but pneumovirus-specific T-cell responses also are important mediators of severe immunopathology. In this study we determined whether memory- or pre-existing, transferred virus-specific CD8 + T-cells provide protection against PVM-induced disease. We show that during infection with a sublethal dose of PVM, both natural killer (NK) cells and CD8 + T-cells expand relatively late. Induction of CD8 + T-cell memory against a single CD8 + T-cell epitope, by dendritic cell (DC)-peptide immunization, leads to partial protection against PVM challenge and prevents Th2 differentiation of PVM-induced CD4 T-cells. In addition, adoptively transferred PVM-specific CD8 + T-cells, covering the entire PVM-specific CD8 + T-cell repertoire, provide partial protection from PVM-induced disease. From these data we infer that antigen-specific memory CD8 + T-cells offer significant protection to PVM-induced disease. Thus, CD8 + T-cells, despite being a major cause of PVM-associated pathology during primary infection, may offer promising targets of a protective pneumovirus vaccine
Transport spectroscopy in a time-modulated open quantum dot
We have investigated the time-modulated coherent quantum transport phenomena
in a ballistic open quantum dot. The conductance and the electron dwell
time in the dots are calculated by a time-dependent mode-matching method. Under
high-frequency modulation, the traversing electrons are found to exhibit three
types of resonant scatterings. They are intersideband scatterings: into
quasibound states in the dots, into true bound states in the dots, and into
quasibound states just beneath the subband threshold in the leads. Dip
structures or fano structures in are their signatures. Our results show
structures due to 2 intersideband processes. At the above
scattering resonances, we have estimated, according to our dwell time
calculation, the number of round-trip scatterings that the traversing electrons
undertake between the two dot openings.Comment: 8 pages, 5 figure
Dissipation of vibration in rough contact
The relationship which links the normal vibration occurring during the sliding of rough surfaces and the nominal contact area is investigated. Two regimes are found. In the first one, the vibrational level does not depend on the contact area, while in the second one, it is propor- tional to the contact area. A theoretical model is proposed. It is based on the assumption that the vibrational level results from a competition between two processes of vibration damping, the internal damping of the material and the contact damping occurring at the interface
Phenomenological Consequences of Singlet Neutrinos
In this paper, we study the phenomenology of right-handed neutrino
isosinglets. We consider the general situation where the neutrino masses are
not necessarily given by , where and are the Dirac and
Majorana mass terms respectively. The consequent mixing between the light and
heavy neutrinos is then not suppressed, and we treat it as an independent
parameter in the analysis. It turns out that conversion is an important
experiment in placing limits on the heavy mass scale () and the mixing.
Mixings among light neutrinos are constrained by neutrinoless double beta
decay, as well as by solar and atmospheric neutrino experiments. Detailed
one-loop calculations for lepton number violating vertices are provided.Comment: Revtex file,TRI-PP-94-1,VPI-IHEP-94-1, 23 pages, a compressed for 8
figures is appende
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