103,834 research outputs found
A New Viewpoint to the Discrete Approximation: Discrete Yang-Fourier Transforms of Discrete-time Fractal Signal
It is suggest that a new fractal model for the Yang-Fourier transforms of
discrete approximation based on local fractional calculus and the Discrete
Yang-Fourier transforms are investigated in detail.Comment: Key words: local fractional calculus, fractal, Yang Fourier
transforms, discrete approximation, discrete Yang-Fourier transforms
corrected sectio
Applications of local fractional calculus to engineering in fractal time-space: Local fractional differential equations with local fractional derivative
This paper presents a better approach to model an engineering problem in
fractal-time space based on local fractional calculus. Some examples are given
to elucidate to establish governing equations with local fractional derivative.Comment: 10 page
Note on the super inflation in loop quantum cosmology
Phenomenological effect of the super-inflation in loop quantum cosmology
(LQC) is discussed. We investigate the case that the Universe is filled with
the interacting field between massive scalar field and radiation. Considering
the damping coefficient as a constant, the changes of the scale factor
during super-inflation with four different initial conditions are discussed,
and we find that the changes of the scale factor depends on the initial values
of energy density of the scalar field and radiation at the bounce point. But no
matter which initial condition is chosen, the radiation always dominated at the
late time. Moreover, we investigate whether the super-inflation can provide
enough e-folding number. For the super-inflation starts from the quantum bounce
point, the initial value of Hubble parameter , then it is possible
to solve the flatness problem and horizon problem. As an example, following the
method of \cite{Amoros-prd} to calculate particle horizon on the condition that
the radiation dominated at bounce point, and we find that the Universe has had
enough time to be homogeneous and isotopic.Comment: 9 pages, 4 figures. Physics Letters B, online publication complete:
13-NOV-201
Linear perturbations in Eddington-inspired Born-Infeld gravity
We study the full linear perturbations of a homogeneous and isotropic
spacetime in the Eddington-inspired Born-Infeld gravity. The stability of the
perturbations are analyzed in the Eddington regime. We find that, for positive
, the scalar modes are stable in the infinite wavelength limit ()
but unstable for . The vector modes are stable and the tensor mode is
unstable in the Eddington regime, independent of the wave vector . However,
these modes are unstable and hence cause the instabilities for negative
.Comment: 11 pages, no figures, published versio
Lossy Quantum Optical Metrology with Squeezed States
We study the precise phase estimation using squeezed states with photon
losses present. Our exact quantum Fisher information calculation shows
significant quantum enhancement and thus reveals the benchmark for practical
quantum metrology in this noisy scenario. However, we find that the existing
parity measurement scheme [P.M. Anisimov et al, Phys. Rev. Lett. 104, 103602
(2010)] behaves worse than even classical cases given very small losses, unless
we take an appropriate loss dependent phase shift. Using our formulae, the two
optimized aspects including the pre-detection phase shift and the consequent
light intensity of a tradeoff strategy for photon resource arrangement can be
both calculated. Therefore our result makes it possible to experimentally
realize quantum metrology of phase estimation with squeezed states.Comment: Published versio
The role of the diffusive protons in the gamma-ray emission of supernova remnant RX J1713.73946 --- a two-zone model
RX~J1713.73946 is a prototype in the -ray-bright supernova
remnants (SNRs) and is in continuing debates on its hadronic versus leptonic
origin of the -ray emission. We explore the role played by the
diffusive relativistic protons that escape from the SNR shock wave in the
-ray emission, apart from the high-energy particles' emission from the
inside of the SNR. In the scenario that the SNR shock propagates in a clumpy
molecular cavity, we consider that the-ray emission from the inside of
the SNR may arise either from the inverse Compton scattering or from the
interaction between the trapped energetic protons and the shocked clumps. The
dominant origin between them depends on the electron-to-proton number ratio.
The diffusive protons that escaped from the shock wave during the expansion
history can provide an outer hadronic -ray component by bombarding the
surrounding dense matter. The broadband spectrum can be well explained by this
two-zone model, in which the -ray emission from the inside governs the
TeV band, while the outer emission component substantially contributes to the
GeV -rays. The two-zone model can also explain the TeV -ray
radial brightness profile that significantly stretches beyond the nonthermal
X-ray-emitting region. In the calculation, we present a simplified algorithm
for Li & Chen's (2010) "accumulative diffusion" model for escaping protons and
apply the Markov Chain Monte Carlo method to constrain the physical parameters.Comment: 18 pages (including 3 figures and 2 tables), accepted for publication
in Ap
Nonreciprocal Directional Dichroism Induced by the Quantum Metric Dipole
We identify the quantum metric dipole as the geometric origin of the
nonreciprocal directional dichroism which describes the change in the
refractive index upon reversing the light propagation direction. Specifically,
we find that the static limit of the nonreciprocal directional dichroism
corresponds to a quadrupolar transport current from the quantum metric dipole,
in response to a quadrupolar electric field. Moreover, at finite frequency, we
demonstrate that the steepest slope of the averaged quantum metric dipole
determines a peak. Finally, we illustrate both features in a low-energy model
m-Order Time Optimal Control Synthesis Function of Discrete System
In this paper, first of all, we introduce the basic concepts of generating
function in combinatorics and some combinatorial identities. In order to
facilitate the understanding of m-order time optimal control synthesis function
of discrete system (referred as m-order synthesis function), secondly, we
introduce the derivation process and control ideas of 2nd-order synthesis
function, and then deduce in detail the m-order synthesis function by means of
generating function. By use of the m-order tracking-form synthesis function
with filter factor, the methods of signal extraction and its predictive
compensation are presented in this paper, and their immunity and effectiveness
are verified by numerical simulation.Comment: 22 pages,13 figures. arXiv admin note: substantial text overlap with
arXiv:1806.0310
Effects of Pressure on the Electronic Structures of LaOFeP
We studied the electronic structures of LaOFeP under applied pressure using
first-principles calculations. The electronic density of states at the Fermi
level decreases continuously with increasing pressure. The electron branches of
Fermi surfaces are rather robust to pressure, while the hole branches change
significantly. Two hole surfaces shrink into small ellipsoid-like surfaces and
disappear finally, at which the applied pressure is ~ 74.7 GPa. The pressure
response can be understood by the band structures around the Fermi level.
Comparative studies reveal that the disappearance of hole surfaces is mainly
due to the compression of the FeP layer along the c-axis of unit cell.Comment: 26 pages, 9 figure
Singular perturbations with multiple poles of the simple polynomials
In this article, we study the dynamics of the following family of rational
maps with one parameter: \begin{equation*} f_\lambda(z)=
z^n+\frac{\lambda^2}{z^n-\lambda}, \end{equation*} where and
. This family of rational maps can be viewed as a
singular perturbations of the simple polynomial . We give a
characterization of the topological properties of the Julia sets of the family
according to the dynamical behaviors of the orbits of the free
critical points.Comment: 15 pages, 5 figures, to appear in Qualitative Theory of Dynamical
System
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