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Stability of LRS Bianchi type-I cosmological models in f(R,T)-gravity

Research in Astronomy and Astrophysics 2019年第4期19卷 63-76页

作者： Umesh Kumar Sharma Rashid Zia anirudh pradhan Aroon Beesham Department of Mathematics Institute of Applied Sciences & Humanities GLA University Department of Mathematical Sciences University of Zululand

This paper examines the stability of the transition from the early decelerating stage of the Universe to the recent accelerating stage for the perfect fluid cosmological locally rotationally symmetric(LRS) Bianchi-I model in f(R, T) theory. To determine the solution of field equations, the idea of a timevarying deceleration parameter(DP) which yields a scale factor, for which the Universe attains a phase transition scenario and is consistent with recent cosmological observations, is used. The time-dependent DP yields a scale factor a=exp■, where β and k are respectively arbitrary and integration constants. By using the recent cons_traints(H_0 _= 73.8, and q_0 =-0.54) from Type Ia Supernova(SN Ia) data in combination with Baryonic Acoustic Oscillations(BAO) and Cosmic Microwave Background(CMB) observations(Giostri et al.), we obtain the values of β = 0.0062 and k = 0.000016 for which we have derived a cosmological model from the early decelerated phase to the present accelerating phase. By applying_ other r_ecent constraints(H_0 = 73.8, q_0 =-0.73) from SNe Ia Union data(Cunha), we obtain the values of β = 0.0036 and k = 0.000084 for which we have derived a cosmological model in the accelerating phase only. We have compared both models with experimental data. The stability of the background solution has been examined also for the metric perturbations alongside the properties of future singularities in a Universe ruled by dark energy with phantom type fluid. We demonstrate the presence of a stable fixed point with a condition of state ω <-1 and numerically affirm this is really a late-time attractor in the ghost overwhelmed Universe. Some physical and geometric properties of the model are found and examined.

关键词： LRS Bianchi-I Universe Time-dependent deceleration parameter f(R,T) gravity theory Transit universe

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Higher Dimensional Strange Quark Matter Coupled to the String Cloud with Electromagnetic Field Admitting One Parameter Group of Conformal Motion

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Chinese Physics Letters 2007年第10期24卷 3013-3016页

作者： pradhan anirudh KHADEKAR G.S. MISHRA Mukesh Kumar KUMBHARE Sarojt Department of Mathematics Hindu Post-graduate College Zamania-232331 Ghazipur India Department of Mathematics R. T. M. Nagpur University Mahatma Jyotiba Phule Educational Campus Amravati Road Nagpur-440033 India

We solve Einstein＇s field equations in higher-dimensional spherically symmetric spacetime with strange quark matter attached to the string cloud, assuming one parameter group of con formal motions. The solutions match with the higher-dimensional Reissner-Nordstroem metric on the boundary at r=ro. The features of the solutions are also discussed in the framework of higher-dimensional spacetime.

关键词： coated conductor buffer layer self-epitaxy CeO2

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Charged quark stars in f(R,T)gravity

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Chinese Physics C 2022年第11期46卷 308-317页

作者： Juan M.Z.Pretel Takol Tangphati Ayan Banerjee anirudh pradhan Centro Brasileiro de Pesquisas Físicas Rua Dr.Xavier Sigaud150 URCARio de Janeiro CEP 22290-180RJBrazil Theoretical and Computational Physics Group Theoretical and Computational Science Center(TaCS)Faculty of ScienceKing Mongkut’s University of Technology Thonburi126 Prachauthid Rd.Bangkok 10140Thailand Astrophysics and Cosmology Research Unit School of MathematicsStatistics and Computer ScienceUniversity of KwaZulu-NatalPrivate Bag X54001Durban 4000South Africa Centre for Cosmology Astrophysics and Space ScienceGLA UniversityMathura-281406Uttar PradeshIndia

Recent advances in nuclear theory and new astrophysical observations have led to the need for specific theoretical models applicable to dense-matter physics *** chromodynamics(QCD)predicts the existence of non-nucleonic degrees of freedom at high densities in neutron-star matter,such as quark *** a confining quark matter model,which consists of homogeneous,neutral 3-flavor interacting quark matter with O(m_(s)^(4))corrections,we examine the structure of compact stars composed of a charged perfect fluid in the context of f(R,T)*** system of differential equations describing the structure of charged compact stars has been derived and numerically solved for a gravity model with f(R,T)=R+2β*** simplicity,we assumed that the charge density is proportional to the energy density,namely,ρ_(ch)=αρ.It is demonstrated that the matter-geometry coupling constant β and charge parameter α affect the total gravitational mass and the radius of the star.

关键词： charged stars f(R T)gravity

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Massive String Cosmology in Bianchi Type Ⅲ Space-Time with Electromagnetic Field

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Communications in Theoretical Physics 2010年第11期 950-956页

作者： anirudh pradhan Suman Lata H.Amirhashchi Department of Mathematics Hindu Post-graduate College Department of Physics Mahshahr Islamic Azad University

Exact solution of Einstein＇s field equations is obtained for massive string cosmological model of Bianchi III space-time using the technique given by Letelier （1983） in presence of perfect fluid and electromagnetic field. To get the deterministic solution of the field equations the expansion 0 in the model is considered as proportional to the eigen value σ2^2of the shear tensor σi^j and also the fluid obeys the barotropic equation of state. It is observed that in early stage of the evolution of the universe string dominates over the particle whereas the universe is dominated by massive string at the late time. It is also observed that the string phase of the universe disappears in our model because particle density becomes negative. Some physical and geometric properties of the model are also discussed.

关键词： massive string exact solution perfect fluid electromagnetic field

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