Iranian Journal of Astronomy and AstrophysicsIranian Journal of Astronomy and Astrophysics
http://ijaa.du.ac.ir/
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http://ijaa.du.ac.ir/
Feed provided by Iranian Journal of Astronomy and Astrophysics. Click to visit.Calculation of the relativistic bulk tensor and shear tensor of relativistic accretion flows in ...
http://ijaa.du.ac.ir/article_122_22.html
In this paper, we calculate the relativistic bulk tensor and shear tensor of the relativistic accretion ows in the Kerr metric, overall and without any approximation. We obtain the relations of all components of the relativistic bulk and shear tensor in terms of components of four-velocity and its derivatives, Christoffel symbols and metric components in the BLF. Then, these components are derived in the equa-torial plane. To see the behavior of the relativistic bulk tensor and shear tensor in the relativistic accretion disks around the rotating black holes, we introduce a radial form for the radial component of the four-velocity in the LNRF; therefore, all components of the bulk and shear tensor are derived in the BLF. Figures of non-zero components of the bulk tensor and shear tensor are shown for some states. We use the radial model to study the importance and in uence of the relativistic bulk tensor in the accretion disks around the rotating black holes. Also, we see that in some cases bulk tensor may be important and comparable with the shear tensor. Especially, we see that bulk tensor in the inner radii is more important.Thu, 30 Nov 2017 20:30:00 +0100Finite temperature correlation function of two dissipative massive scalar ﬁelds: Thermoﬁeld ...
http://ijaa.du.ac.ir/article_123_22.html
The present paper aims at investigating the manner of two dissipative massive scalar ﬁelds. Two massive scalar ﬁelds that interact with a reservoir were considered and a reservoir was modeled by continuum Klein-Gordon ﬁelds. The Lagrangian of the total system was canonically quantized and the dynamics of the system was determined using the Euler-Lagrange equation. Then, the explicit form of the quantum massive scalar ﬁelds in long-time limit were observed. The propagator of the system and correlation functions were calculated at ﬁnite temperature in the thermoﬁeld dynamics formalizem.Thu, 30 Nov 2017 20:30:00 +0100Introducing Stable Real Non-Topological Solitary Wave Solutions in 1+1 Dimensions
http://ijaa.du.ac.ir/article_124_22.html
By adding a proper term to the Lagrangian density of a real non-linear KG system with a proposed non-topological unstable solitary wave solution, its stability guaranteed appreciably. This additional term in the new modiﬁed Lagrangian density behaves like a strong internal force which stands against any arbitrary small deformation in the proposed non-topological solitary wave solution.Thu, 30 Nov 2017 20:30:00 +0100Multi fluidity and Solitary wave stability in cold quark matter: core of dense astrophysical objects
http://ijaa.du.ac.ir/article_125_22.html
Considering the magneto-hydrodynamic equations in a non-relativistic multi uid framework, we study the behavior of small amplitude perturbations in cold quark matter. Magneto-hydrodynamic equations, along with a suitable equation of state for the cold quark matter, are expanded using the reductive perturbation method. It is shown that in small amplitude approximation, such a medium should be considered as a multi- uid system. The result is a nonlinear wave equation which complies with a modied form of the derivative nonlinear Schrodinger equation instead of the KdV equation. Considering the magnetic eld which is supported by the Maxwell's equations, we show that the complete set of equations, create stable solitary waves. An interesting result is the existence of an electric eld component along the direction of magnetic eld which causes a small charge separability in the medium. Properties of this solitonic solution are studied by considering different values for the environmental characters such as background mass density and strength of the magnetic eld (at the scale of compact stars).Thu, 30 Nov 2017 20:30:00 +0100Oscillations of a Giant Solar Tornado
http://ijaa.du.ac.ir/article_126_22.html
Solar magnetic tornadoes are known to be one of the mass and energy transport mechanisms from the lower solar atmosphere into the upper layers of the solar corona. A bright spiral structure with two arms is observed using high-cadence EUV images of 171, 193 and 304 Ǻ channels of Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) on 10th of July 2011 for three hours. The structure studied here looks bright in front of dark background emissions. The rotational energy budget of this tornado is estimated using three different approaches. Results showed the rotational energy ranges between 1.95×1018 erg to 3.36×1019 erg. After correcting for the solar differential rotation, the oscillatory behaviour of the structure is studied using FFT technique. Results show four different regimes of oscillations: 3-min, 5-6 min, 8-11 min, and 15-17 min. The showed origin of each of these oscillations are discussed.Thu, 30 Nov 2017 20:30:00 +0100