5,709 research outputs found
A Non-Mainstream Viewpoint on Apparent Superluminal Phenomena in AGN Jet
The group velocity of light in material around the AGN jet is acquiescently
one (c as a unit), but this is only a hypothesis. Here, we re-derive apparent
superluminal and Doppler formulas for the general case (it is assumed that the
group velocity of light in the uniform and isotropic medium around a jet (a
beaming model) is not necessarily equal to one, e.g., Araudo et al. (2010)
thought that there may be dense clouds around AGN jet base), and show that the
group velocity of light close to one could seriously affect apparent
superluminal phenomena and Doppler effect in the AGN jet (when the viewing
angle and Lorentz factor take some appropriate values).Comment: 4 pages, 2 figures, new version accepted for publication in Journal
of Astrophysics and Astronom
Null geodesics and gravitational lensing in a nonsingular spacetime
In this paper, the null geodesics and gravitational lensing in a nonsingular
spacetime are investigated. According to the nature of the null geodesics, the
spacetime is divided into several cases. In the weak deflection limit, we find
the influence of the nonsingularity parameter on the positions and
magnifications of the images is negligible. In the strong deflection limit, the
coefficients and observables for the gravitational lensing in a nonsingular
black hole background and a weakly nonsingular spacetime are obtained.
Comparing these results, we find that, in a weakly nonsingular spacetime, the
relativistic images have smaller angular position and relative magnification,
but larger angular separation than that of a nonsingular black hole. These
results might offer a way to probe the spacetime nonsingularity parameter and
put a bound on it by the astronomical instruments in the near future.Comment: 15 pages, 5 figures, 1 tabl
A Ricardian Model with Endogenous Comparative Advantage and Endogenous Trade Policy Regimes
This paper develops a general equilibrium model with transaction costs and endogenous and exogenous comparative advantages. In the model, the governments are allowed to choose between tariff war, tariff negotiation, and laissez faire regimes. The model shows that the level of division of labor and the volume of trade increase as transaction conditions improve. In the process of moving to a high level of division of labour, a country may receive more gains from trade even if its terms of trade deteriorate. This is because an expansion of the network size of division of labour can generate productivity gains that outweigh the adverse effect of the terms of trade deterioration. When a high level of division of labor occurs in general equilibrium, if both countries play a Nash tariff game, a tariff war may break out, which can dissipate all the gains from trade. Facing this risk, all governments would prefer trade negotiations to a trade war. A Nash tariff negotiation would result in zero tariff rates. If a medium level of division of labor occurs in general equilibrium, then unilateral tariff protection and unilateral laissez faire policies would coexist. The result provides a plausible story about the evolution of trade policy regimes, and highlights the importance of trade negotiations in achieving trade liberalization.inframarginal analysis of trade theory, Ricardo model, dual structure, underdevelopment
An asymmetrical synchrotron model for knots in the 3C 273 jet
To interpret the emission of knots in the 3C 273 jet from radio to X-rays, we
propose a synchrotron model in which, owing to the shock compression effect,
the injection spectra from a shock into the upstream and downstream emission
regions are asymmetric. Our model could well explain the spectral energy
distributions of knots in the 3C 273 jet, and predictions regarding the knots
spectra could be tested by future observations.Comment: 9 pages, 1 figure, 1 table, new version accepted for publication in
Ap
Gravity Localization and Effective Newtonian Potential for Bent Thick Branes
In this letter, we first investigate the gravity localization and mass
spectrum of gravity KK modes on de Sitter and Anti-de Sitter thick branes.
Then, the effective Newtonian gravitational potentials for these bent branes
are discussed by the two typical examples. The corrections of the Newtonian
potential turns out to be at small for both
cases. These corrections are very different from that of the Randall-Sundrum
brane model .Comment: 6 pages, 2 figure
Nuclear geometry effect and transport coefficient in semi-inclusive lepton-production of hadrons off nuclei
Hadron production in semi-inclusive deep-inelastic scattering of leptons from
nuclei is an ideal tool to determine and constrain the transport coefficient in
cold nuclear matter. The leading-order computations for hadron multiplicity
ratios are performed by means of the SW quenching weights and the analytic
parameterizations of quenching weights based on BDMPS formalism. The
theoretical results are compared to the HERMES positively charged pions
production data with the quarks hadronization occurring outside the nucleus.
With considering the nuclear geometry effect on hadron production, our
predictions are in good agreement with the experimental measurements. The
extracted transport parameter from the global fit is shown to be for the SW quenching weight without the finite energy
corrections. As for the analytic parameterization of BDMPS quenching weight
without the quark energy E dependence, the computed transport coefficient is
. It is found that the nuclear geometry effect
has a significant impact on the transport coefficient in cold nuclear matter.
It is necessary to consider the detailed nuclear geometry in studying the
semi-inclusive hadron production in deep inelastic scattering on nuclear
targets.Comment: 14 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1310.569
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