183,583 research outputs found
Experimentally realizable control fields in quantum Lyapunov control
As a hybrid of techniques from open-loop and feedback control, Lyapunov
control has the advantage that it is free from the measurement-induced
decoherence but it includes the system's instantaneous message in the control
loop. Often, the Lyapunov control is confronted with time delay in the control
fields and difficulty in practical implementations of the control. In this
paper, we study the effect of time-delay on the Lyapunov control, and explore
the possibility of replacing the control field with a pulse train or a
bang-bang signal. The efficiency of the Lyapunov control is also presented
through examining the convergence time of the controlled system. These results
suggest that the Lyapunov control is robust gainst time delay, easy to realize
and effective for high-dimensional quantum systems
Exclusive Decays and CP Violation in the General two-Higgs-doublet Model
We calculate all the branching ratios and direct CP violations of
decays in a most general two-Higgs-doublet model with spontaneous CP violation.
As the model has rich CP-violating sources, it is shown that the new physics
effects to direct CP violations and branching ratios in some channels can be
significant when adopting the generalized factorization approach to evaluate
the hadronic matrix elements, which provides good signals for probing new
physics beyond the SM in the future B experiments.Comment: 21 page
Calibrating the {\alpha} parameter of convective efficiency using observed stellar properties
Context. Synthetic model atmosphere calculations are still the most commonly
used tool when determining precise stellar parameters and stellar chemical
compositions. Besides three-dimensional models that consistently solve for
hydrodynamic processes, one-dimensional models that use an approximation for
convective energy transport play the major role.
Aims. We use modern Balmer-line formation theory as well as spectral energy
distribution (SED) measurements for the Sun and Procyon to calibrate the model
parameter {\alpha} that describes the efficiency of convection in our 1D
models. Convection was calibrated over a significant range in parameter space,
reaching from F-K along the main sequence and sampling the turnoff and giant
branch over a wide range of metallicities. This calibration was compared to
theoretical evaluations and allowed an accurate modeling of stellar
atmospheres.
Methods. We used Balmer-line fitting and SED fits to determine the convective
efficiency parameter {\alpha}. Both methods are sensitive to the structure and
temperature stratification of the deeper photosphere.
Results. While SED fits do not allow a precise determination of the
convective parameter for the Sun and Procyon, they both favor values
significantly higher than 1.0. Balmer-line fitting, which we find to be more
sensitive, suggests that the convective efficiency parameter {\alpha} is
2.0 for the main sequence and quickly decreases to 1.0 for
evolved stars. These results are highly consistent with predictions from 3D
models. While the values on the main sequence fit predictions very well,
measurements suggest that the decrease of convective efficiency as stars evolve
to the giant branch is more dramatic than predicted by models.Comment: 14 pages, 16 figures, accepted for publication in A&
Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation
A left-right symmetric model with two Higgs bi-doublet is shown to be a
consistent model for both spontaneous P and CP violation. The flavor changing
neutral currents can be suppressed by the mechanism of approximate global U(1)
family symmetry. We calculate the constraints from neural meson mass
difference and demonstrate that a right-handed gauge boson
contribution in box-diagrams with mass well below 1 TeV is allowed due to a
cancellation caused by a light charged Higgs boson with a mass range GeV. The contribution to can be suppressed from
appropriate choice of additional CP phases appearing in the right-handed
Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully
consistent with mass difference , and the mixing-induced CP
violation quantity , which is usually difficult for the
model with only one Higgs bi-doublet. The new physics beyond the standard model
can be directly searched at the colliders LHC and ILC.Comment: 25 pages, 6 figures, typos corrected, 1 figure added, published
versio
Hawking Radiation of an Arbitrarily Accelerating Kinnersley Black Hole: Spin-Acceleration Coupling Effect
The Hawking radiation of Weyl neutrinos in an arbitrarily accelerating
Kinnersley black hole is investigated by using a method of the generalized
tortoise coordinate transformation. Both the location and temperature of the
event horizon depend on the time and on the angles. They coincide with previous
results, but the thermal radiation spectrum of massless spinor particles
displays a kind of spin-acceleration coupling effect.Comment: 8 pages, no figure, revtex 4.0, revisted version with typesetting
errors and misprint correcte
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