20,117 research outputs found

    The effect of the motion of the Sun on the light-time in interplanetary relativistic experiments

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    In 2002 a measurement of the effect of solar gravity upon the phase of coherent microwave beams passing near the Sun has been carried out with the Cassini mission, allowing a very accurate measurement of the PPN parameter γ\gamma. The data have been analyzed with NASA's Orbit Determination Program (ODP) in the Barycentric Celestial Reference System, in which the Sun moves around the centre of mass of the solar system with a velocity v⊙v_\odot of about 10 m/sec; the question arises, what correction this implies for the predicted phase shift. After a review of the way the ODP works, we set the problem in the framework of Lorentz (and Galilean) transformations and evaluate the correction; it is several orders of magnitude below our experimental accuracy. We also discuss a recent paper \cite{kopeikin07}, which claims wrong and much larger corrections, and clarify the reasons for the discrepancy.Comment: Final version accepted by Classical and Quantum Gravity (8 Jan. 2008

    Non-minimal coupling of photons and axions

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    We establish a new self-consistent system of equations accounting for a non-minimal interaction of gravitational, electromagnetic and axion fields. The procedure is based on a non-minimal extension of the standard Einstein-Maxwell-axion action. The general properties of a ten-parameter family of non-minimal linear models are discussed. We apply this theory to the models with pp-wave symmetry and consider propagation of electromagnetic waves non-minimally coupled to the gravitational and axion fields. We focus on exact solutions of electrodynamic equations, which describe quasi-minimal and non-minimal optical activity induced by the axion field. We also discuss empirical constraints on coupling parameters from astrophysical birefringence and polarization rotation observations.Comment: 31 pages, 2 Tables; replaced with the final version published in Classical and Quantum Gravit

    Non-ancient solution of the Ricci flow

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    For any complete noncompact Ka¨\ddot{a}hler manifold with nonnegative and bounded holomorphic bisectional curvature,we provide the necessary and sufficient condition for non-ancient solution to the Ricci flow in this paper.Comment: seven pages, latex fil

    Extended axion electrodynamics: Optical activity induced by nonstationary dark matter

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    We establish a new self-consistent Einstein-Maxwell-axion model based on the Lagrangian, which is linear in the pseudoscalar (axion) field and its four-gradient and includes the four-vector of macroscopic velocity of the axion system as a whole. We consider extended equations of the axion electrodynamics, modified gravity field equations, and discuss nonstationary effects in the phenomenon of optical activity induced by axions.Comment: 6 pages, 0 figures, accepted for publication in the Journal Gravitation and Cosmology, reported at the 14th Russian Gravitational Conference (Ulyanovsk, 2011

    Incorporating UPFC model into the power system toolbox of theMATLAB for transient stability study

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    In this paper, power frequency model for unified power flow controller (UPFC) is presented with its DC link capacitor dynamics included. A novel interface of UPFC to AC network for transient stability study is then suggested and realised using Power System Toolbox (PST) of MATLAB. The control strategies for UPFC shunt and series elements are also discussed. Computer results on a 4-generator interconnected test power system show that the convergence and accuracy of the suggested interface are challenging and the suggested interface makes it very easy to incorporate the UPFC model into the conventional transient stability programme. The results also show that the UPFC control strategy had strong impacts on the performance of UPFC.published_or_final_versio
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