Cosmological principle and torsion

Tsamparlis, Michael

doi:10.1016/0375-9601(79)90265-2

Cited by 111 publications

(135 citation statements)

References 3 publications

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“…A similar course was taken with regard to cosmological models in f (R) gravity in order to see which features of the Friedmann universes of GR were retained in these larger theories [6]. One framework that has gained momentum in recent years is that of teleparallel gravity (TEGR) [7,8] and its modification, the f (T ) teleparallel theory [9][10][11]. This theory of gravity provides a different perspective on the mechanism of gravity.…”

Section: Introductionmentioning

confidence: 99%

Stability of the Kasner universe in f(T) gravity

2018

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f (T ) gravity theory offers an alternative context in which to consider gravitational interactions where torsion, rather than curvature, is the mechanism by which gravitation is communicated. We investigate the stability of the Kasner solution with several forms of the arbitrary lagrangian function examined within the f (T ) context. This is a Bianchi type-I vacuum solution with anisotropic expansion factors. In the f (T ) gravity setting, the solution must conform to a set of conditions in order to continue to be a vacuum solution of the generalized field equations. With this solution in hand, the perturbed field equations are determined for power-law and exponential forms of the f (T ) function. We find that the point which describes the Kasner solution is a saddle point which means that the singular solution is unstable. However, we find the de Sitter universe is a late-time attractor. In general relativity, the cosmological constant drives the the isotropization of the spacetime while in this setting the extra f (T ) contributions now provide this impetus.PACS numbers: 98.80.-k, 95.35.+d, 95.36.+x

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Section: Introductionmentioning

confidence: 99%

Stability of the Kasner universe in f(T) gravity

2018

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“…The particle approximation for Dirac fields, however, is not self-consistent [4]. The spin-fluid description also violates the cosmological principle [14]. In this paper, we use the Dirac form of the spin tensor for fermionic matter, s ijk = s [ijk] [2,6,12], which follows directly from the Dirac Lagrangian and is consistent with the cosmological principle [15].…”

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confidence: 99%

Nonsingular, big-bounce cosmology from spinor-torsion coupling

2012

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The Einstein-Cartan-Sciama-Kibble theory of gravity removes the constraint of general relativity that the affine connection be symmetric by regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between the torsion tensor and Dirac spinors generates a spin-spin interaction which is significant in fermionic matter at extremely high densities. We show that such an interaction averts the unphysical big-bang singularity, replacing it with a cusp-like bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic.

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“…Moreover, in order to preserve the FRW metric structure in a standard cosmological setup, one requires the tensor mode Q µνσ of torsion to vanish altogether, and the vector modes T µ and A µ to have only their temporal components existent. 30,59 Also since the torsion field is generally taken to be massless, 24,32 one expects the scalar field source φ, of its trace mode T µ to be massless as well. However, the pseudotrace mode of torsion, A µ , may effectively lead to a scalar field potential…”

Section: The General Mst Formalism In the Cosmological Setupmentioning

confidence: 99%

Dynamical system analysis of dark energy models in scalar coupled Metric-Torsion theories

Bhatia

Sur

2017

Int. J. Mod. Phys. D

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We study the phase space dynamics of cosmological models in the theoretical formulations of non-minimal metric-torsion couplings with a scalar field, and investigate in particular the critical points which yield stable solutions exhibiting cosmic acceleration driven by the dark energy. The latter is so defined that it effectively has no direct interaction with the cosmological fluid, although in an equivalent scalar-tensor cosmological setup the scalar field interacts with the fluid (which we consider to be the pressureless dust). Determining the conditions for the existence of the stable critical points we check their physical viability in both Einstein and Jordan frames. We also verify that in either of these frames, the evolution of the universe at the corresponding stable points matches with that given by the respective exact solutions we have found in an earlier work (arXiv:1611.00654 [gr-qc]). We not only examine the regions of physical relevance in the phase space when the coupling parameter is varied, but also demonstrate the evolution profiles of the cosmological parameters of interest along fiducial trajectories in the effectively non-interacting scenarios, in both Einstein and Jordan frames.

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Cosmological principle and torsion

Cited by 111 publications

References 3 publications

Stability of the Kasner universe in f(T) gravity

Stability of the Kasner universe in f(T) gravity

Nonsingular, big-bounce cosmology from spinor-torsion coupling

Dynamical system analysis of dark energy models in scalar coupled Metric-Torsion theories

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