2021-06-19T10:37:06Z
http://ijaa.du.ac.ir/?_action=export&rf=summon&issue=30
Iranian Journal of Astronomy and Astrophysics
IJAA
2322-4924
2322-4924
2017
4
3
Calculation of the relativistic bulk tensor and shear tensor of relativistic accretion flows in the Kerr metric.
Mahboobe
Moeen
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.
relativistic viscosity
relativistic bulk tensor
relativistic shear tensor
relativistic shear stress viscosity
black holes accretion disks
relativistic flows
2017
12
01
205
221
http://ijaa.du.ac.ir/article_122_c850f8252ffbb5a2c5bbc939a691b85f.pdf
Iranian Journal of Astronomy and Astrophysics
IJAA
2322-4924
2322-4924
2017
4
3
Finite temperature correlation function of two dissipative massive scalar ﬁelds: Thermoﬁeld approach
Marjan
Jafari
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.
massive scalar ﬁeld
correlation function
dissipative
thermoﬁeld dynamics
2017
12
01
223
230
http://ijaa.du.ac.ir/article_123_f8de2feace3527d44611adc4fc6ff487.pdf
Iranian Journal of Astronomy and Astrophysics
IJAA
2322-4924
2322-4924
2017
4
3
Introducing Stable Real Non-Topological Solitary Wave Solutions in 1+1 Dimensions
Mohammad
mohammadi
Ali Reza
Olamaei
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.
non-linear KG systems
non-topological
solitary wave solutions
stability
soliton
2017
12
01
231
244
http://ijaa.du.ac.ir/article_124_7471a0364c7fc6b178e36236c967ef18.pdf
Iranian Journal of Astronomy and Astrophysics
IJAA
2322-4924
2322-4924
2017
4
3
Multi fluidity and Solitary wave stability in cold quark matter: core of dense astrophysical objects
Azam
Ghaani
Parvin
Eslami
Mohsen
Sarbishaei
Kurosh
Javidan
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).
keyword
2017
12
01
245
260
http://ijaa.du.ac.ir/article_125_04ef1add2900a30c735cb4975b69c650.pdf
Iranian Journal of Astronomy and Astrophysics
IJAA
2322-4924
2322-4924
2017
4
3
Oscillations of a Giant Solar Tornado
Fatemeh
Hashemi-Nasab
Neda
Dadashi
Nasibeh
Alipour-Rad
YousefAli
Abedini
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.
Sun: Corona
Sun: Tornado
Sun: UV radiation
Sun: Oscillations
2017
12
01
261
271
http://ijaa.du.ac.ir/article_126_eaa05200a6d65c33dd1a39e503451a34.pdf
Iranian Journal of Astronomy and Astrophysics
IJAA
2322-4924
2322-4924
2017
4
3
Thermal measurement induced disturbance in the Bose-Hubbard Hamiltonian
Hamed
Jafarzadeh
Hakimeh
Jaghouri
We study measurement induced disturbance (MID) in a qutrit –qutrit system with considering the effect of the external magnetic field, nonlinear and linear coupling constants and temperature. We show that all of these parameters have effective roles in MID. We also investigate the effect of finite external magnetic fields direction as parallel and anti-parallel on MID, and find some interesting results.
qutrit
measurement induced disturbance
Bose-Hubbard Hamiltonian
2017
12
01
273
282
http://ijaa.du.ac.ir/article_129_589fb68d43c6d60852ad90eb7755f445.pdf