The Physics Society of IranIranian Journal of Physics Research1682-69575320191126Dark matter or the other dynamicsDark matter or the other dynamics113119670FAY. SoboutiJournal Article20191126 Allowing the energy of a gravitational field to serve partially as its own source allows gravitating bodies to exhibit stronger fields, as if they were more massive. Depending on degree of compaction of the body, the field could be one to five times larger than the Newtonian field. This is a comfortable range of increase in field strength and may prove to be of convenience in the study of velocity curves of spirals, of velocity dispersions in clusters of galaxies and in interpreting the Tully-Fisher or Faber-Jackson relations in galaxies or systems of galaxies. The revised gravitation admits of superposition principle but only approximately in systems whose components are widely separated. The revised dynamics admits of the equivalence principle in that, the effective force acting on a test particle is derived from a potential, and could be elimhnated in a freely falling frame of reference. Allowing the energy of a gravitational field to serve partially as its own source allows gravitating bodies to exhibit stronger fields, as if they were more massive. Depending on degree of compaction of the body, the field could be one to five times larger than the Newtonian field. This is a comfortable range of increase in field strength and may prove to be of convenience in the study of velocity curves of spirals, of velocity dispersions in clusters of galaxies and in interpreting the Tully-Fisher or Faber-Jackson relations in galaxies or systems of galaxies. The revised gravitation admits of superposition principle but only approximately in systems whose components are widely separated. The revised dynamics admits of the equivalence principle in that, the effective force acting on a test particle is derived from a potential, and could be elimhnated in a freely falling frame of reference.https://ijpr.iut.ac.ir/article_670_17c276c8e723eb46aef576537e9d56d0.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126Designing and making a differential astronomical seeing monitorDesigning and making a differential astronomical seeing monitor121128671FAA. DarudiS. NasiriJournal Article20191126 Which place is an appropriate site for the construction of the Iranian National Observatory (INO)? In this paper part of the site selection process is reported. The emphasis is on the measuring of the seeing parameter for the pre-selected regions. These regions are examined by meteorological and geophysical studies and finally Kashan, Kerman, Qom and Ferdows sites were selected among 31 regions. To decide on the best site the seeing parameter had to be measured for the regions. To measure this parameter, one needs an astronomical seeing monitor. Designing and making a kind of seeing monitor and preparing the corresponding software is demonstrated and analysing of a sample of seeing data is discussed. Which place is an appropriate site for the construction of the Iranian National Observatory (INO)? In this paper part of the site selection process is reported. The emphasis is on the measuring of the seeing parameter for the pre-selected regions. These regions are examined by meteorological and geophysical studies and finally Kashan, Kerman, Qom and Ferdows sites were selected among 31 regions. To decide on the best site the seeing parameter had to be measured for the regions. To measure this parameter, one needs an astronomical seeing monitor. Designing and making a kind of seeing monitor and preparing the corresponding software is demonstrated and analysing of a sample of seeing data is discussed.https://ijpr.iut.ac.ir/article_671_5dd9db5e033da9c6fb5ba83c7a7ebea9.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126Junction conditions in stepwise Sine-Gordon equation and soltion collisionsJunction conditions in stepwise Sine-Gordon equation and soltion collisions129134672FAN. RiaziJournal Article20191126 The stepwise Sine-Gordon equation in which the value of the system parameter is different for negative and positive value of the scalar field is investigated. By applying appropriate junction conditions, the relation between solition velocities before and after collision is derived. It turns out that a heavy soliton anti-soliton pair can transform into a light pair moving at right velocities. We call this phenomenon “soliton gun”. Some of the result which were obtained before numerically, are derived analytically in this paper. The stepwise Sine-Gordon equation in which the value of the system parameter is different for negative and positive value of the scalar field is investigated. By applying appropriate junction conditions, the relation between solition velocities before and after collision is derived. It turns out that a heavy soliton anti-soliton pair can transform into a light pair moving at right velocities. We call this phenomenon “soliton gun”. Some of the result which were obtained before numerically, are derived analytically in this paper.https://ijpr.iut.ac.ir/article_672_2dea61eed4bceec564a00115c4d21334.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126Scattering of electromagnetic waves by a traversable wormholeScattering of electromagnetic waves by a traversable wormhole135144673FAB. Nasr EsfahaniS. DehdashtiM. EshaghiJournal Article20191126 Replacing the wormhole geometry with an equivalent medium using the perturbation theory of scattering and the Born approximation, we have calculated the differential scattering cross section of electromagnetic waves by a traversable wormhole. It is shown that scattering at long wavelenghts can essentially distinguish wormhole from ordinary scattering object. Some of the zeros of the scattering cross section are determined which can be used for estimating the radius of the throat of wormholes. The known result that in this kind of scattering the linear polarization remains unchanged is verified here. Replacing the wormhole geometry with an equivalent medium using the perturbation theory of scattering and the Born approximation, we have calculated the differential scattering cross section of electromagnetic waves by a traversable wormhole. It is shown that scattering at long wavelenghts can essentially distinguish wormhole from ordinary scattering object. Some of the zeros of the scattering cross section are determined which can be used for estimating the radius of the throat of wormholes. The known result that in this kind of scattering the linear polarization remains unchanged is verified here.https://ijpr.iut.ac.ir/article_673_9f396fe44e7c05c16873b05ec425cbad.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126Resonant absorption and damping of hydromagnetic waves in solar coronaResonant absorption and damping of hydromagnetic waves in solar corona145152674FAS. NasiriL. YousefiJournal Article20191126 Although, the hot solar corona was discovered more than sixty years ago, however, the exact dissipation mechanism that heats the corona is still unknown. Resonant absorption and damping of Alfven waves appear to be one of the major candidates in this respect. The corona is highly structured and inhomogeneous medium, containing a large number of discrete magnetic loops. In this paper a cylindrical magnetic flux tube with a specified density profile is considered, and the ideal equation of motion in coronal condition is obtained. The problem is reduced to solving a wave equation for the component of magnetic perturbation along the tube axis. The mathematical formalism is identical with that of the propagation of electromagnetic waves in optical fibers with a varying index of refraction through the cross section of the fiber. The ideal equations of magnetic and velocity fields in the global modes are singular and are solved numerically, using a modified shooting scheme. Resistive and viscous dissipation rates as an exponential time decay of disturbances are obtained. The results show that the amount of energy produced in the resonant layer inside the tube seems to be responsible for heating the corona. Although, the hot solar corona was discovered more than sixty years ago, however, the exact dissipation mechanism that heats the corona is still unknown. Resonant absorption and damping of Alfven waves appear to be one of the major candidates in this respect. The corona is highly structured and inhomogeneous medium, containing a large number of discrete magnetic loops. In this paper a cylindrical magnetic flux tube with a specified density profile is considered, and the ideal equation of motion in coronal condition is obtained. The problem is reduced to solving a wave equation for the component of magnetic perturbation along the tube axis. The mathematical formalism is identical with that of the propagation of electromagnetic waves in optical fibers with a varying index of refraction through the cross section of the fiber. The ideal equations of magnetic and velocity fields in the global modes are singular and are solved numerically, using a modified shooting scheme. Resistive and viscous dissipation rates as an exponential time decay of disturbances are obtained. The results show that the amount of energy produced in the resonant layer inside the tube seems to be responsible for heating the corona.https://ijpr.iut.ac.ir/article_674_0d7de1aca9299fe63f3e0041f02638a3.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126A class of exact solutions of higher derivative gravity in four dimensionsA class of exact solutions of higher derivative gravity in four dimensions153156675FAM. H. DehghaniH. Mohammad PourJournal Article20191126 In this paper we consider the action of higher derivative gravity up to the second order terms in the scalars made from the Ricci scalar, Ricci and Riemann tensors. We use the Bach- Lanczos identity of the Weyl tensor in four dimensions and show that the solutions of 4-dimensional Einstein equations with cosmological constant term in vacuum, which are known as Einstein metrics, satisfy the field equations of higher derivative gravity. We also find that the field equations of higher derivative gravity are not satisfied by the solutions of Einstein equations in higher dimensions or in the presence of matter. In this paper we consider the action of higher derivative gravity up to the second order terms in the scalars made from the Ricci scalar, Ricci and Riemann tensors. We use the Bach- Lanczos identity of the Weyl tensor in four dimensions and show that the solutions of 4-dimensional Einstein equations with cosmological constant term in vacuum, which are known as Einstein metrics, satisfy the field equations of higher derivative gravity. We also find that the field equations of higher derivative gravity are not satisfied by the solutions of Einstein equations in higher dimensions or in the presence of matter.https://ijpr.iut.ac.ir/article_675_8fecb20817b3847419bb3de39a609afe.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126On quantizing gravity and geometrizing quantum mechanicsOn quantizing gravity and geometrizing quantum mechanics157157676FAAli MostafazadehJournal Article20191126 We elaborate on some recent results on a solution of the Hilbert-space problem in minisuperspace quantum cosmology and discuss the consequences of making the (geometry of the) Hilbert space of ordinary nonrelativistic quantum systems time-dependent. The latter reveals a remarkable similarity between Quantum Mechanics and General Relativity. We elaborate on some recent results on a solution of the Hilbert-space problem in minisuperspace quantum cosmology and discuss the consequences of making the (geometry of the) Hilbert space of ordinary nonrelativistic quantum systems time-dependent. The latter reveals a remarkable similarity between Quantum Mechanics and General Relativity.https://ijpr.iut.ac.ir/article_676_dc6a70712a252123c40d2adba6a11d84.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126Spherical null shells within the distributional formalismSpherical null shells within the distributional formalism158158677FASamad KhakshourniaReza MansouriJournal Article20191126 A null thin shell immersed in a generic spherically symmetric space-time is studied within the distributional formalism. It has been shown that the distributional formalism leads to the same result as the conventional Barrabes-Israel formalism. A null thin shell immersed in a generic spherically symmetric space-time is studied within the distributional formalism. It has been shown that the distributional formalism leads to the same result as the conventional Barrabes-Israel formalism.https://ijpr.iut.ac.ir/article_677_71a3cb155f8dc89bf3d0365288219936.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126On synchronization of clocks in general space-timesOn synchronization of clocks in general space-times159159678FAM. R. H KhajehpourR. MansouriJournal Article20191126 Einstein and transport synchronizations of infinitesimally spaced and distant clocks are considered in a general Riemannian space-time. It is shown that infinitesimally spaced clocks can always be synchronized. In general one can not find observers for whom distant clock are Einstein synchronized but transport synchronized observers do always exit. Whenever both procedures are possible, they are equivalent. Einstein and transport synchronizations of infinitesimally spaced and distant clocks are considered in a general Riemannian space-time. It is shown that infinitesimally spaced clocks can always be synchronized. In general one can not find observers for whom distant clock are Einstein synchronized but transport synchronized observers do always exit. Whenever both procedures are possible, they are equivalent.https://ijpr.iut.ac.ir/article_678_9fe8593a8a330607d76796b35c64c600.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126Thermodynamics of rotating black branes in gravity with first order string correctionsThermodynamics of rotating black branes in gravity with first order string corrections160160679FAM. H. DehghaniJournal Article20191126 In this paper, the rotating black brane solutions with zero curvature horizon of classical gravity with first order string corrections are introduced. Although these solutions are not asymptotically anti de Sitter, one can use the counterterm method in order to compute the conserved quantities of these solutions. Here, by reviewing the counterterm method for asymptotically anti de Sitter spacetimes, the conserved quantities of these rotating solutions are computed. Also a Smarr-type formula for the mass as a function of the entropy and the angular momenta is obtained, and it is shown that the conserved and thermodynamic quantities satisfy the first law of thermodynamics. Finally, a stability analysis in the canonical ensemble is performed, and it is shown that the system is thermally stable. This is in commensurable with the fact that there is no Hawking-Page phase transition for black object with zero curvature horizon. In this paper, the rotating black brane solutions with zero curvature horizon of classical gravity with first order string corrections are introduced. Although these solutions are not asymptotically anti de Sitter, one can use the counterterm method in order to compute the conserved quantities of these solutions. Here, by reviewing the counterterm method for asymptotically anti de Sitter spacetimes, the conserved quantities of these rotating solutions are computed. Also a Smarr-type formula for the mass as a function of the entropy and the angular momenta is obtained, and it is shown that the conserved and thermodynamic quantities satisfy the first law of thermodynamics. Finally, a stability analysis in the canonical ensemble is performed, and it is shown that the system is thermally stable. This is in commensurable with the fact that there is no Hawking-Page phase transition for black object with zero curvature horizon.https://ijpr.iut.ac.ir/article_679_ca9c267dad0305d1a6308d2a0cf1c39c.pdfThe Physics Society of IranIranian Journal of Physics Research1682-69575320191126Solar rotation gravitational momentsSolar rotation gravitational moments161161680FAA. AjabshirizadehZ. FazelJournal Article20191126 Gravitational multipole moments of the Sun are still poorly known. Theoretically, the difficulty is mainly due to the differential rotation for which the velocity rate varies both on the surface and with the depth. From an observational point of view, the multipole moments cannot be directly measured. However, recent progresses have been made proving the existence of a strong radial differential rotation in a thin layer near the solar surface (the leptocline). Applying the theory of rotating stars, we will first compute values of J2 and J4 taking into account the radial gradient of rotation, then we will compare these values with the existing ones, giving a more complete review. We will explain some astrophysical outcomes, mainly on the relativistic Post Newtonian parameters. Finally we will conclude by indicating how space experiments (balloon SDS flights, Golf NG, Beppi-Colombo, Gaia...) will be essential to unambiguously determine these parameters. Gravitational multipole moments of the Sun are still poorly known. Theoretically, the difficulty is mainly due to the differential rotation for which the velocity rate varies both on the surface and with the depth. From an observational point of view, the multipole moments cannot be directly measured. However, recent progresses have been made proving the existence of a strong radial differential rotation in a thin layer near the solar surface (the leptocline). Applying the theory of rotating stars, we will first compute values of J2 and J4 taking into account the radial gradient of rotation, then we will compare these values with the existing ones, giving a more complete review. We will explain some astrophysical outcomes, mainly on the relativistic Post Newtonian parameters. Finally we will conclude by indicating how space experiments (balloon SDS flights, Golf NG, Beppi-Colombo, Gaia...) will be essential to unambiguously determine these parameters.https://ijpr.iut.ac.ir/article_680_fccb3cdc9acc14a6e70a12f74560c026.pdf