Int J Theor Phys (2007) 46: 2774–2787 DOI 10.1007/s10773-007-9388-0 Plane Symmetric Viscous Fluid Cosmological Models with Varying Λ-Term Anirudh Pradhan · Purnima Pandey · Kanti Jotania · Mahesh Kumar Yadav Published online: 10 May 2007 © Springer Science+Business Media, LLC 2007 Abstract Plane symmetric viscous fluid cosmological models of the universe with a vari- able cosmological term are investigated. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear viscosity is to be proportional to rate of expansion in the model. We have also obtained a special model in which the shear viscosity is assumed to be zero. The cosmological constant Λ is found to be a decreasing function of time and a positive which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed. Keywords Cosmology · Viscous models · Variable cosmological term 1 Introduction In modern cosmological theories, a dynamic cosmological term Λ(t) remains a focal point of interest as it solves the cosmological constant problem in a natural way. There are signif- icant observational evidence for the detection of Einstein’s cosmological constant, Λ or a A. Pradhan ( ) · P. Pandey Department of Mathematics, Hindu Post-graduate College, Zamania 232 331, Ghazipur, India e-mail: pradhan@iucaa.ernet.in A. Pradhan ( ) e-mail: acpradhan@yahoo.com P. Pandey e-mail: purnima_pandey2001@yahoo.com K. Jotania Department of Physics, Faculty of Science, The M.S. University of Baroda, Vadodara 390 002, Gujarat, India e-mail: kanti@iucaa.ernet.in M.K. Yadav Department of Mathematics, Sobhasaria Engineering College, NH-11, Sikar 332 001, India e-mail: yadavmk@iucaa.ernet.in