Bianchi type I string dust cosmological models in the presence and absence of magnetic field in the frame work of Lyra geometry are investigated. To get the deterministic model of the universe, we assume that the eige...Bianchi type I string dust cosmological models in the presence and absence of magnetic field in the frame work of Lyra geometry are investigated. To get the deterministic model of the universe, we assume that the eigenvalue （σ^11） of shear tensor （σ^ii） is proportional to expansion （θ）. This leads to A = （BC）^n, where A, B, C are metric potentials and n is a constant. To discuss the results in terms of cosmic time t, we have considered n = 1. The physical and geometrical aspects＇ of the models and singularities in the models are also discussed.展开更多
The C-field cosmological model based on the Hoyle-Narlikar theory with variable gravitational constant G is investigated. To obtain the deterministic value of C=dC/dt we present certain constant values for integration...The C-field cosmological model based on the Hoyle-Narlikar theory with variable gravitational constant G is investigated. To obtain the deterministic value of C=dC/dt we present certain constant values for integration constants. The creation field is proportional to time. G and p （density） decrease with time and the universe represents an expanding universe. The creation field increases as time increases. We find C=√1/2πf t where f〉0,Thus C=1 when f=1/2π〉0.展开更多
The locally rotationally symmetric(LRS)Bianchi type-II inflationary cosmological model is investigated for massless scalar field with flat potential and time varyingΛ.To obtain the deterministic solution,it is assume...The locally rotationally symmetric(LRS)Bianchi type-II inflationary cosmological model is investigated for massless scalar field with flat potential and time varyingΛ.To obtain the deterministic solution,it is assumed that scale factor is a(t)~e^(Ht) as we considered previously for Bianchi type-I spacetime andΛ~a^(-2) as considered by Chen and Wu,where H is the Hubble constant and effective potential V(φ)=const;φHigg's field.It is shown that such a time varyingΛleads to no conflict with existing observations.However,it does change the predictions of standard cosmology in the matter-dominated phase and alleviates some problems in reconciling observations with the inflationary scenario.The model represents anisotropic spacetime in general.However,the model isotropizes for large values of t andβ=3H^(2),whereβis constant.The physical and geometrical aspects of the model in the context of an inflationary scenario is also discussed.展开更多
文摘Bianchi type I string dust cosmological models in the presence and absence of magnetic field in the frame work of Lyra geometry are investigated. To get the deterministic model of the universe, we assume that the eigenvalue （σ^11） of shear tensor （σ^ii） is proportional to expansion （θ）. This leads to A = （BC）^n, where A, B, C are metric potentials and n is a constant. To discuss the results in terms of cosmic time t, we have considered n = 1. The physical and geometrical aspects＇ of the models and singularities in the models are also discussed.
文摘The C-field cosmological model based on the Hoyle-Narlikar theory with variable gravitational constant G is investigated. To obtain the deterministic value of C=dC/dt we present certain constant values for integration constants. The creation field is proportional to time. G and p （density） decrease with time and the universe represents an expanding universe. The creation field increases as time increases. We find C=√1/2πf t where f〉0,Thus C=1 when f=1/2π〉0.
文摘The locally rotationally symmetric(LRS)Bianchi type-II inflationary cosmological model is investigated for massless scalar field with flat potential and time varyingΛ.To obtain the deterministic solution,it is assumed that scale factor is a(t)~e^(Ht) as we considered previously for Bianchi type-I spacetime andΛ~a^(-2) as considered by Chen and Wu,where H is the Hubble constant and effective potential V(φ)=const;φHigg's field.It is shown that such a time varyingΛleads to no conflict with existing observations.However,it does change the predictions of standard cosmology in the matter-dominated phase and alleviates some problems in reconciling observations with the inflationary scenario.The model represents anisotropic spacetime in general.However,the model isotropizes for large values of t andβ=3H^(2),whereβis constant.The physical and geometrical aspects of the model in the context of an inflationary scenario is also discussed.
