eng
Damghan University
Astronomical Society of Iran
Iranian Journal of Astronomy and Astrophysics
2322-4924
2383-403X
2017-04-01
4
1
1
8
10.22128/ijaa.2017.84
84
Noether Symmetry in f(T) Theory at the anisotropic universe
عنوان
A. Aghamohammadi
a.aghamohamadi@iausdj.ac.ir
1
Sanandaj Branch, Islamic Azad University, Sanandaj, Iran;
As it is well known, symmetry plays a crucial role in the theoretical physics. On other hand, the Noether symmetry is a useful procedure to select models motivated at a fundamental level, and to discover the exact solution to the given lagrangian. In this work, Noether symmetry in f(T) theory on a spatially homogeneous and anisotropic Bianchi type I universe is considered. We discuss the Lagrangian formalism of f(T ) theory in anisotropic universe. The point-like Lagrangian is clearly constructed.The explicit form of f(T) theory and the corresponding exact solution are found by requirement of Noether symmetry and Noether charge. A power-law f(T), the same as the FRW universe, can satisfy the required Noether symmetry in the anisotropic universe with power- law scale factor. It is regarded that positive expansion is satisfied by a constrain between parameters.
http://ijaa.du.ac.ir/article_84_3d11a75bdbcbb1c17f437303622835b1.pdf
Noether symmetry
anisotropic Bianchi type I universe
modified theories of gravity
f(T) gravity
eng
Damghan University
Astronomical Society of Iran
Iranian Journal of Astronomy and Astrophysics
2322-4924
2383-403X
2017-04-01
4
1
9
17
10.22128/ijaa.2017.91
91
Effect of random telegraph noise on entanglement and nonlocality of a qubit-qutrit system
عنوان
Hakimeh Jaghouri
1
Samira Nazifkar
2
Quchan University of Advanced Technology, Quchan, Iran
Department of Physics, University of Neyshabur, Neyshabur, Iran
We study the evolution of entanglement and nonlocality of a non-interacting qubit-qutrit system under the eﬀect of random telegraph noise (RTN) in independent and common environments in Markovian and non-Markovian regimes. We investigate the dynamics of qubit-qutrit system for diﬀerent initial states. These systems could be existed in far astronomical objects. A monotone decay of the nonlocality (entanglement) is found in the Markov regime, while for non-Markovian noise, phenomena of sudden change (death) and revival occurs. We ﬁnd that the preserving nonlocality (entanglement) depends on initial state of the system in common and independent environments; so, we can not strictly conclude that independent or common environments are more robust against the noise.
http://ijaa.du.ac.ir/article_91_b5bee8f95aabb0536aa0909083a32fc5.pdf
keyword
eng
Damghan University
Astronomical Society of Iran
Iranian Journal of Astronomy and Astrophysics
2322-4924
2383-403X
2017-04-01
4
1
19
36
10.22128/ijaa.2017.92
92
Pulsating red giant and supergiant stars in the Local Group dwarf galaxy Andromeda I
عنوان
Elham Saremi
saremi@birjand.ac.ir
1
Abbas Abedi
aabedi@birjand.ac.ir
2
Atefeh Javadi
atefeh@ipm.ir
3
Jacco van Loon
j.t.van.loon@keele.ac.uk
4
Habib Khosroshahi
5
School of Physics, Birjand University, Birjand, P.O.Box 97175-615, Iran;
School of Physics, Birjand University, Birjand, P.O.Box 97175-615, Iran;
School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, P.O.Box 19395-5531, Iran;
Lennard-Jones Laboratories, Keele University, ST5 5BG, UK
School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, P.O.Box 19395-5531, Iran;
We have conducted an optical long-term monitoring survey of the majority of dwarf galaxies in the Local Group, with the Isaac Newton Telescope (INT), to identify the long period variable (LPV) stars. LPV stars vary on timescales of months to years, and reach the largest amplitudes of their brightness variations at optical wavelengths, due to the changing temperature. They trace stellar populations as young as ~ 30 Myr to as old as ~ 10 Gyr whose identification is one of the best ways to reconstruct the star formation history.<br /> The system of galactic satellites of the large Andromeda spiral galaxy (M31) forms one of the key targets of our monitoring survey. In this first paper in the series, we present the first results from the survey in the form of a census of LPV stars in Andromeda I (And I) dwarf galaxy.<br /> Photometry was obtained for 10585 stars in a 0.07 square degree field, of which 116 stars<br /> were found to be variable, most of which are Asymptotic Giant Branch (AGB) stars.<br /> Our data were matched to mid-infrared photometry from the Spitzer Space Telescope, and to optical catalogues of variable stars from the Hubble Space Telescope.
http://ijaa.du.ac.ir/article_92_bc6ca8daf6e604a9634da5dde859f833.pdf
stars: evolution
stars: red giants
supergiants
stars: mass-loss
stars: oscillations
galaxies: individual: Andromeda I
galaxies: stellar content
eng
Damghan University
Astronomical Society of Iran
Iranian Journal of Astronomy and Astrophysics
2322-4924
2383-403X
2017-04-01
4
1
37
43
10.22128/ijaa.2017.105
105
A Simplified Solution for Advection Dominated Accretion Flows with Outflow
مقاله
Seyede Tahere Kashfi
1
Shahram Abbassi
abbassi@um.ac.ir
2
Department of Physics, Ferdowsi University of Mashhad, Mashhad, Iran
Department of Physics, Ferdowsi University of Mashhad, Mashhad, Iran
The existence of outflow in the advection dominated accretion flows has been confirmed by both numerical simulations and observations. The outow models for ADAF have been investigated by several groups with a simple self similar solution. But this solution is inaccurate at the inner regions and can not explain the emitted spectrum of the flow; so, it is necessary to obtain a global solution for ADAFs with outflow. In this paper, we use a simplified global solution to study the structure of ADAF in the presence of outflow. In this method which is proposed by Yuan et al (2008, hereafter YMN08), the radial momentum equation is replaced by a simple algebraic relation between angular velocity and Keplerian angular velocity to avoid the difficulty of the calculation of global solution. We consider the radial dependence for mass accretion rate <em>M</em> =<em>M</em> <em><sub>out</sub></em>(<em>r/r</em><em><sub>out</sub></em>)<em><sup>s</sup></em>where <em>s </em>is a constant and we do not change the other dynamical equations. We investigate the variation of physical quantity of accretion flow which is caused by outflow. The results that we obtained comply with our expectations from the influence of outflow on the structure of accretion flow.
http://ijaa.du.ac.ir/article_105_a49a64c684d30c77c4e2f0be27a74ba2.pdf
accretion
accretion disks
black hole
global solution
outflow
eng
Damghan University
Astronomical Society of Iran
Iranian Journal of Astronomy and Astrophysics
2322-4924
2383-403X
2017-04-01
4
1
45
56
10.22128/ijaa.2017.106
106
Modeling Magnetic Field in Heavy ion Collisions Using Two Diﬀerent Nuclear Charge Density Distributions
عنوان
Susan Abbas Nejad
susanabbasnejad@gmail.com
1
Supervisor: Dr. Umut Gursoy
2
University College Utrecht, Utrecht, The Netherlands
Department of Physics, Utrecht University, Utrecht, The Netherlands
By studying the properties of matter during heavy-ion collisions, a better understanding of the Quark-Gluon plasma is possible. One of the main areas of this study is the calculation of the magnetic ﬁeld, particularly how the values of conductivity aﬀects this ﬁeld and how the ﬁeld strength changes with proper time. In matching the theoretical calculations with results obtained in lab, two diﬀerent models for charge density distribution inside ions is used. In this study, after explanation of some theoretical background, the magnetic ﬁeld contribution of the spectators and participants in Pb-Pb ion collision is calculated in a conductive medium and vacuum. Results are compared using two diﬀerent nuclear charge density models.
http://ijaa.du.ac.ir/article_106_c8c2df32ce5297813a9d26aa61bd9df9.pdf
Quark-Gluon Plasma
QCD
Heavy Ion Collisions
Electromagnetic ﬁeld
Nuclear density distributions
eng
Damghan University
Astronomical Society of Iran
Iranian Journal of Astronomy and Astrophysics
2322-4924
2383-403X
2017-04-01
4
1
57
68
10.22128/ijaa.2017.108
108
Soliton-like Solutions of the Complex Non-linear Klein-Gordon Systems in 1 + 1 Dimensions
Soliton-like Solutions of the Complex Non-linear Klein-Gordon Systems in 1 + 1 Dimensions
Mohammad mohammadi
physmohammadi@pgu.ac.ir
1
Ali Reza Olamaei
olamaei@jahromu.ac.ir
2
Physics Department, Persian Gulf University, Bushehr 75169, Iran.
Jahrom University, Jahrom 74135-111, Iran
In this paper, we present soliton-like solutions of the non-linear complex Klein-Gordon systems in 1+1 dimensions. We will use polar representation to introduce three different soliton-like solutions including, complex kinks (anti-kinks), radiative profiles, and localized wave-packets. Complex kinks (anti-kinks) are topological objects with zero electrical charges. Radiative profiles are objects that move at the speed of light and therefore, have a zero rest mass. They can be created in kink-anti-kink collisions and vice versa. Localized wave packet solutions are non-topological objects for which wave and particle behavior are reconciled in a classical way. For localized wave packet solutions, the trivial initial phase imposes an uncertainty on the collision fates.
http://ijaa.du.ac.ir/article_108_1dac6703cd70c6208c97d18ea09f4ff9.pdf
complex
non-linear
Klein-Gordon
soliton
uncertainty
kink
radiative-profile
wave-packet