Presence Of Cosmological Term Research Articles

Interaction of anisotropic dark energy fluid with perfect fluid in the presence of cosmological term Λ

Considering the locally rotationally symmetric (LRS) Bianchi type-I metric with cosmological constant [Formula: see text], Einstein’s field equations are discussed based on the background of anisotropic fluid. We assumed the condition A = B[Formula: see text] for the metric potentials A and B, where m is a positive constant to obtain the viable model of the Universe. It is found that [Formula: see text] is positive and inversely proportional to time. The values of matter-energy density [Formula: see text], dark energy density [Formula: see text] and deceleration parameter q are found to be consistent with the values of WMAP observations. State finder parameters and anisotropic deviation parameter are also investigated. It is also observed that the derived model is an accelerating, shearing and non-rotating Universe. Some of the asymptotic and geometrical behaviors of the derived models are investigated with the age of the Universe.

Kantowski-Sachs viscous fluid cosmological model with a varying \Lambda

We study the Kantowski-Sachs cosmological model filled with viscous fluid in the presence of cosmological term \Lambda. To get a deterministic solution, a condition between metric potentials is used. The viscous coefficient of bulk viscous fluid is assumed to be a power function of mass density, whereas coefficient of shear viscosity is considered proportional to scale of expansion in the model. It is found that the cosmological constant \Lambda is positive and is a decreasing function of time, which is supported by results from recent supernova observations. Some physical and geometrical properties of the models are also discussed.

From Ginzburg–Landau to Hilbert–Einstein via Yamabe

In this paper, based on some mathematical results obtained by Yamabe, Osgood, Phillips and Sarnak, we demonstrate that in dimensions three and higher the famous Ginzburg–Landau equations used in the theory of phase transitions can be obtained (without any approximations) by minimization of the Riemannian-type Hilbert–Einstein action functional for pure gravity in the presence of cosmological term. We use this observation in order to bring to completion the work by Lifshitz (done in 1941) on group-theoretical refinements of the Landau theory of phase transitions. In addition, this observation allows us to develop a systematic extension to higher dimensions of known string-theoretic path integral methods developed for calculation of observables in two-dimensional conformal field theories.