Original scientific paper
A new class of Bianchi type I viscous fluid universe with a time dependent cosmological term
A Pradhan
; Department of Mathematics, Hindu Post-graduate College, Zamania-232 331, Ghazipur, India
Anju Rai
; Department of Mathematics, Hindu Post-graduate College, Zamania-232 331, Ghazipur, India
Saeed Otarod
; Department of Physics, Yasouj University, Yasouj, Iran
Abstract
A new class of Bianchi type I viscous-fluid cosmological models with a variable cosmological constant are investigated in which the expansion is considered only in two directions, i.e. one of the Hubble parameter (H1 = A4/A) is zero. We have considered four cases: (i) coefficients of bulk (ξ) and shear (η) viscosity are taken as constant, (ii) ξ and η are considered to be inversely dependent on time, (iii) Λ is taken as inverse square of t and (iv) ξ and η are considered as proportional to scale of expansion in the model. The cosmological constant Λ is found to be positive and is a decreasing function of time which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed.
Keywords
cosmology; Bianchi type I universe; viscous fluid models; variable cosmological constant
Hrčak ID:
304906
URI
Publication date:
1.9.2008.
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