{"title":"天琴座几何中周期时变减速参数中的弦宇宙学场景","authors":"V. Gore, A. Dixit, D. Chouhan","doi":"10.1139/cjp-2022-0203","DOIUrl":null,"url":null,"abstract":"In this paper, we have studied the bulk viscous fluid connected with string cosmological model in a higher dimensional (five dimensions) Bianchi type-III space–time in the framework of Lyra’s manifold. To get the deterministic solution of the field equations, we assume two physically appropriate conditions: ( i) θ in the model parameter that is proportional to the eigen value of [Formula: see text] of the shear tensor [Formula: see text] and ( ii) the periodic time-varying deceleration parameter q specified as q = mcos ( kt) − 1, where m, k > 0. In this paper, we have studied the periodic time-varying behaviour of a few quantities, such as the deceleration parameter q, the energy density ρ, the proper pressure p, the string tension density λ, the total pressure [Formula: see text], the energy density for particle ρp, and the displacement vector β( t), and we have discussed the physical significance of these quantities. It has been found that in the early stages of the universe’s evolution, string prevails over particles, whereas the universe is dominated by massive string at late time. It is also noted that the string phase of the cosmos does not vanish in the model since particle density is constantly positive throughout the universe’s history. In normal gauge treatment, β( t) acts like cosmological constant (Λ), and the solutions are compatible with observations. For the stability analysis, we have investigated the nature of various energy conditions (ECs). The positive behaviour of DEC indicates the model’s validation; on the other hand, SEC and WEC are violating, indicating the universe’s accelerated expansion.","PeriodicalId":9413,"journal":{"name":"Canadian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":1.1000,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"String cosmological scenario in periodic time-varying deceleration parameter in Lyra geometry\",\"authors\":\"V. Gore, A. Dixit, D. Chouhan\",\"doi\":\"10.1139/cjp-2022-0203\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"In this paper, we have studied the bulk viscous fluid connected with string cosmological model in a higher dimensional (five dimensions) Bianchi type-III space–time in the framework of Lyra’s manifold. To get the deterministic solution of the field equations, we assume two physically appropriate conditions: ( i) θ in the model parameter that is proportional to the eigen value of [Formula: see text] of the shear tensor [Formula: see text] and ( ii) the periodic time-varying deceleration parameter q specified as q = mcos ( kt) − 1, where m, k > 0. In this paper, we have studied the periodic time-varying behaviour of a few quantities, such as the deceleration parameter q, the energy density ρ, the proper pressure p, the string tension density λ, the total pressure [Formula: see text], the energy density for particle ρp, and the displacement vector β( t), and we have discussed the physical significance of these quantities. It has been found that in the early stages of the universe’s evolution, string prevails over particles, whereas the universe is dominated by massive string at late time. It is also noted that the string phase of the cosmos does not vanish in the model since particle density is constantly positive throughout the universe’s history. In normal gauge treatment, β( t) acts like cosmological constant (Λ), and the solutions are compatible with observations. For the stability analysis, we have investigated the nature of various energy conditions (ECs). 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引用次数: 0
摘要
本文在Lyra流形的框架下,研究了高维(五维)Bianchi - iii型时空中体积黏性流体与弦宇宙学模型的连接。为了得到场方程的确定性解,我们假设了两个物理上适当的条件:(i)模型参数中的θ与剪切张量[公式:见文][公式:见文]的特征值成正比;(ii)周期性时变减速参数q指定为q = mcos (kt)−1,其中m, k > 0。本文研究了减速参数q、能量密度ρ、固有压力p、弦张力密度λ、总压力[公式:见文]、粒子能量密度ρp、位移矢量β(t)等物理量的周期性时变行为,并讨论了这些物理量的物理意义。人们已经发现,在宇宙演化的早期阶段,弦压倒了粒子,而宇宙在后期则由大质量弦主导。我们还注意到,宇宙的弦相在模型中不会消失,因为粒子密度在整个宇宙历史中一直是正的。在标准规范处理中,β(t)的作用类似于宇宙常数(Λ),其解与观测结果相一致。对于稳定性分析,我们研究了各种能量条件(ECs)的性质。DEC的正向行为表明模型的有效性;另一方面,SEC和WEC是违反的,这表明宇宙正在加速膨胀。
String cosmological scenario in periodic time-varying deceleration parameter in Lyra geometry
In this paper, we have studied the bulk viscous fluid connected with string cosmological model in a higher dimensional (five dimensions) Bianchi type-III space–time in the framework of Lyra’s manifold. To get the deterministic solution of the field equations, we assume two physically appropriate conditions: ( i) θ in the model parameter that is proportional to the eigen value of [Formula: see text] of the shear tensor [Formula: see text] and ( ii) the periodic time-varying deceleration parameter q specified as q = mcos ( kt) − 1, where m, k > 0. In this paper, we have studied the periodic time-varying behaviour of a few quantities, such as the deceleration parameter q, the energy density ρ, the proper pressure p, the string tension density λ, the total pressure [Formula: see text], the energy density for particle ρp, and the displacement vector β( t), and we have discussed the physical significance of these quantities. It has been found that in the early stages of the universe’s evolution, string prevails over particles, whereas the universe is dominated by massive string at late time. It is also noted that the string phase of the cosmos does not vanish in the model since particle density is constantly positive throughout the universe’s history. In normal gauge treatment, β( t) acts like cosmological constant (Λ), and the solutions are compatible with observations. For the stability analysis, we have investigated the nature of various energy conditions (ECs). The positive behaviour of DEC indicates the model’s validation; on the other hand, SEC and WEC are violating, indicating the universe’s accelerated expansion.
期刊介绍:
The Canadian Journal of Physics publishes research articles, rapid communications, and review articles that report significant advances in research in physics, including atomic and molecular physics; condensed matter; elementary particles and fields; nuclear physics; gases, fluid dynamics, and plasmas; electromagnetism and optics; mathematical physics; interdisciplinary, classical, and applied physics; relativity and cosmology; physics education research; statistical mechanics and thermodynamics; quantum physics and quantum computing; gravitation and string theory; biophysics; aeronomy and space physics; and astrophysics.