We investigate the cosmological dynamics in teleparallel gravity with nonminimal coupling. We analytically extract several asymptotic solutions and we numerically study the exact phase-space behavior. Comparing the obtained results with the corresponding behavior of nonminimal scalarcurvature theory, we find significant differences, such is the rare stability and the frequent presence of oscillatory behavior.PACS numbers: 04.50. Kd, 95.36.+x

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.

We explore dynamics of cosmological models with a nonminimally coupled scalar field evolving on a spatially flat Friedmann-Lemaître-Robertson-Walker background. We consider cosmological models including the Hilbert-Einstein curvature term and the N degree monomial of the scalar field nonminimally coupled to gravity. The potential of the scalar field is the n degree monomial or polynomial. We describe several qualitatively different types of dynamics depending on values of power indices N and n. We identify that three main possible pictures correspond to n < N , N < n < 2N and n > 2N cases. Some special features connected with the important cases of N = n (including the quadratic potential with quadratic coupling) and n = 2N (which shares its asymptotics with the potential of the Higgs-driven inflation) are described separately. A global qualitative analysis allows us to cover the most interesting cases of small N and n by a limiting number of phase-space diagrams. The influence of the cosmological constant to the global features of dynamics is also studied.

No abstract

We consider the cosmological dynamics of a nonminimally coupled scalar field in scalar-torsion gravity in the presence of hydrodynamical matter. The potential of the scalar field have been chosen as power law with negative index, this type of potentials is usually used in quintessence scenarios. We identify several asymptotic regimes, including de Sitter, kinetic dominance, kinetic tracker, and tracker solutions and study the conditions for their existence and stability. We show that for each combination of coupling constant and potential power index one of the regimes studied in the present paper is stable to the future.