64,745 research outputs found
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
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
A Tensor Completion Approach for Efficient and Robust Fingerprint-based Indoor Localization
The localization technology is important for the development of indoor
location-based services (LBS). The radio frequency (RF) fingerprint-based
localization is one of the most promising approaches. However, it is
challenging to apply this localization to real-world environments since it is
time-consuming and labor-intensive to construct a fingerprint database as a
prior for localization. Another challenge is that the presence of anomaly
readings in the fingerprints reduces the localization accuracy. To address
these two challenges, we propose an efficient and robust indoor localization
approach. First, we model the fingerprint database as a 3-D tensor, which
represents the relationships between fingerprints, locations and indices of
access points. Second, we introduce a tensor decomposition model for robust
fingerprint data recovery, which decomposes a partial observation tensor as the
superposition of a low-rank tensor and a spare anomaly tensor. Third, we
exploit the alternating direction method of multipliers (ADMM) to solve the
convex optimization problem of tensor-nuclear-norm completion for the anomaly
case. Finally, we verify the proposed approach on a ground truth data set
collected in an office building with size 80m times 20m. Experiment results
show that to achieve a same error rate 4%, the sampling rate of our approach is
only 10%, while it is 60% for the state-of-the-art approach. Moreover, the
proposed approach leads to a more accurate localization (nearly 20%, 0.6m
improvement) over the compared approach.Comment: 6 pages, 5 figure
Observational Constraints on Two-field Warm Inflation
We study the two-field warm inflation models with a double quadratic
potential and a linear temperature dependent dissipative coefficient. We
derived the evolution equation of all kinds of perturbations without assuming
slow-roll approximation, and obtained the curvature power spectrum at the end
of inflation with a fully numerical method. Then we compute the scalar spectral
index , tensor-to-scalar ratio for several representative potentials,
and compare our results with observational data. At last, we use Planck data to
constrain the parameters in our models. This work is a natural extension of
single-field warm inflation, and the aim of this work is to present some
features of multi-field warm inflation using a simple two-field model.Comment: 13 pages, 6 figures. Accepted for publication in Physical Review
Two-field Warm Inflation and Its Scalar Perturbations on Large Scales
We explore the homogeneous background dynamics and the evolution of generated
perturbations of cosmological inflation that is driven by multiple scalar
fields interacting with a perfect fluid.Then we apply the method to warm
inflation driven by two scalar fields and a radiation fluid, and present
general results about the evolution of the inflaton and radiation. After
decomposing the perturbations into adiabatic and entropy modes, we give the
equation of motion of adiabatic and entropy perturbations on large scales.
Then, we give numerical results of background and perturbation equations in a
concrete model (the dissipative coefficient ). At last, we
use the most recent observational data to constrain our models and give the
observationally allowed regions of parameters. This work is a natural extension
of warm inflation to multi-field cases.Comment: 10 pages, 4 figure
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
Primordial non-Gaussianity in noncanonical warm inflation
We study the bispectrum of the primordial curvature perturbation on
uniform-density hypersurfaces generated by a kind of the noncanonical warm
inflation, wherein the inflation is provided by a noncanonical scalar inflaton
field that is coupled to radiation through a thermal dissipation effect. We
obtain an analytic form for the nonlinear parameter that describes the
non-Gaussianity in first-order cosmological perturbation theory and analyse the
magnitude of this nonlinear parameter. We make a comparison between our result
and those of the standard inflation and the canonical warm inflation. We also
discuss when the contribution to the non-Gaussianity due to the second-order
perturbation theory becomes more important and what effect can be observed. We
take the Dirac-Born-Infeld (DBI) inflation as a concrete example to find how
the sound speed and the thermal dissipation strength to decide the
non-Gaussianity and to get a lower bound of the sound speed constrained by
PLANCK.Comment: 7 pages, 2 figure
Warm inflation in loop quantum cosmology: a model with a general dissipative coefficient
A general form of warm inflation with the dissipative coefficient
in loop quantum cosmology is
studied. In this case, we obtain conditions for the existence of a warm
inflationary attractor in the context of loop quantum cosmology by using the
method of stability analysis. The two cases when the dissipative coefficient is
independent and dependent on temperature are analyzed
specifically. In the latter case, we use the new power spectrum which should be
used when considering temperature dependence in the dissipative coefficient. We
find that the thermal effect is enhanced in the case . As in the standard
inflation in loop quantum cosmology, we also reach the conclusion that quantum
effect leaves a tiny imprint on the cosmic microwave background (CMB) sky.Comment: 12 pages, accepted for publication in Rhys. Rev.
The diagram category of framed tangles and invariants of quantized symplectic group
In this paper we present a categorical version of the first and second
fundamental theorems of the invariant theory for the quantized symplectic
groups. Our methods depend on the theory of braided strict monoidal categories
which are pivotal, more explicitly the diagram category of framed tangles.Comment: to appear in Sci. China Mat
Consistency of the tachyon warm inflationary universe models
This study concerns the consistency of the tachyon warm inflationary models.
A linear stability analysis is performed to find the slow-roll conditions,
characterized by the potential slow-roll (PSR) parameters, for the existence of
a tachyon warm inflationary attractor in the system. The PSR parameters in the
tachyon warm inflationary models are redefined. Two cases, an exponential
potential and an inverse power-law potential, are studied, when the dissipative
coefficient and , respectively. A
crucial condition is obtained for a tachyon warm inflationary model
characterized by the Hubble slow-roll (HSR) parameter , and the
condition is extendable to some other inflationary models as well. A proper
number of e-folds is obtained in both cases of the tachyon warm inflation, in
contrast to existing works. It is also found that a constant dissipative
coefficient is usually not a suitable assumption for a warm
inflationary model.Comment: 10 pages, 0 figures, accepted for publication in Journal of Cosmology
and Astroparticle Physics (JCAP
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