We investigate the cosmological dynamics of non-minimally coupled scalar field system described by F (φ)R coupling with F (φ) = 1 − ξφ N R(N ≥ 2) and the field potential, V (φ) = V0φ n . We use a generic set of dynamical variables to bring out new asymptotic regimes of the underlying dynamics. However, our dynamical variables miss the most important fixed point− the de Sitter solution. We make use of the original form of system of equations to investigate the issues related to this important solution. In particular, we show that the de-Sitter solution which is a dynamical attractor of the system lies in the region of negative effective gravitational constant GN thereby leading to a ghost dominated universe in future and a transient quintessence(phantom) phase with GN > 0 around the present epoch 1 . We also carry out comparison of the model with other competing models of dark energy such as galileon modified gravity and others.

Abstract. In this paper, we examine observational constraints on the power law cosmology; essentially dependent on two parameters H 0 (Hubble constant) and q (deceleration parameter). We investigate the constraints on these parameters using the latest 28 points of H(z) data and 580 points of Union2.1 compilation data and, compare the results with the results of ΛCDM. We also forecast constraints using a simulated data set for the future JDEM, supernovae survey. Our studies give better insight into power law cosmology than the earlier done analysis by Kumar [arXiv:1109.6924] indicating it tuning well with Union2.1 compilation data but not with H(z) data. However, the constraints obtained on < H 0 > and < q > i.e. H 0 average and q average using the simulated data set for the future JDEM, supernovae survey are found to be inconsistent with the values obtained from the H(z) and Union2.1 compilation data. We also perform the statefinder analysis and find that the power-law cosmological models approach the standard ΛCDM model as q → −1. Finally, we observe that although the power law cosmology explains several prominent features of evolution of the Universe, it fails in details.

In this paper, we study the pre-inflationary dynamics for the power-law potential (V (φ) ∝ φ n ) with n < 2 in the framework of loop quantum cosmology. In the case where the kinetic energy of the inflaton dominates at the initial, the evolution of the universe can always be divided into three different phases prior to reheating: bouncing, transition and slow-roll inflation. During the bouncing phase, the evolution of the expansion factor is independent not only on the initial conditions but also the inflationary potentials, and is given explicitly by an analytical solution. In contrast, for the potential energy dominated initial conditions, this universality is lost. We also obtain total number of e-folds during the slow-roll inflation, whereby physically viable models are identified. In addition, we present phase space analysis for the inflationary potentials under consideration and compare our results with the ones obtained previously for different potentials.

In this paper, we investigate coupled quintessence with scaling potential assuming specific forms of the coupling as A namely, αρ m , βρ φ and σ (ρ m +ρ φ ), and present phase space analysis for three different interacting models. We focus on the attractor solutions that can give rise to late time acceleration with DE / DM of order unity in order to alleviate the coincidence problem.

In this article we explore the pre-inflationary background dynamics of an FLRW universe sourced by a scalar field with monodromy potential in LQC framework. In particular we calculate the number of e-folds, N inf , produced during the slowly rolling phase of the inflation and find out the critical value of the ratio of the kinetic to potential energy, r c w , at the quantum bounce that is required to produce N inf 60. Two different monodromy potentials, namely, linear and quadratic with a modulation term are investigated to this effect. The effects on the value of N inf due to parameters associated with the strength, decay constant and the phase factor of the modulation term are calculated. In addition to this we present the qualitative picture of the background dynamics by carrying out a dynamical system analysis. We produce the phase portraits and carry out a detailed linear stability analysis of the finite fixed points, if any, for each of the potentials.