Torsion Cosmology Research Articles

Phase space analysis of torsion cosmology

In this paper, we study the dynamical stability analysis by considering the torsion field [Formula: see text] which is proportional to the Hubble parameter and barotropic equation-of-state parameter in the framework of the homogenous and isotropic FLRW metric with non-zero torsion in the scenario of dark matter and dark energy interacting terms. We discuss the stability of the critical points corresponding to the eigenvalues in the presence of dust and radiation at quintessence, [Formula: see text]CDM and phantom regimes by utilizing the different linear and nonlinear interaction models which depend on the energy density. As a result, we observe that the first linear model shows the stable behavior throughout the universe for dust and radiation phase. The other linear and nonlinear models show the stable critical points, computing with the eigenvalues at phantom and [Formula: see text]CDM era with the best fit value of interaction strength and coupling constant for dust and radiation.

Matter growth perturbations and cosmography in modified torsion cosmology

We examine the cosmic evolution of the growth of perturbations with respect to matter content at early and recent past era of the Universe under the framework of non-zero torsion cosmology. Some cosmographic parameters are also discussed. To analyze this cosmic scenario, we formulate the cosmic models with two dark matter considerations and apply spherical collapse formalism. We explore that for model-1 (pressureless matter), the density contrast starts growing in early era of the Universe and with the Universe’s overall expansion, density contrast grows faster for different choices of torsion parameter. In model-2 (matter with non-zero pressure), the density contrast shows enormous growth as compared to overall expansion of the Universe for the perturbed region, which indicates the collapse of the perturbed region and formulation of new large scale matter or galaxy. Further, we analyze the behavior of the growth function for both models with different values of torsion parameter. For model-1, the growth function increases smoothly for different choices of torsion parameter but for the model-2 the behavior of the growth function with nonzero DM and torsion significantly deviates from pressureless DM with zero torsion (Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM). We also investigate different cosmographic parameters for both models and analyze their behavior with different choices of torsion parameter and Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM. The results show the power-law expansion rate of the accelerating Universe with respect to redshift function.

Reconstructing Torsion Cosmology from Interacting Holographic Dark Energy Model

We consider a cosmological model in the framework of Einstein–Cartan theory with a single scalar torsion ϕ=ϕ(t) and reconstruct the torsion model corresponding to the holographic dark energy (HDE) density. By studying the corresponding relation between the effective energy density of torsion field ρϕ and holographic dark energy density ρHDE, we naturally obtain a kind of torsion field from the interacting holographic dark energy with interaction term Q=−2ϕρm and ρm is the energy density of matter. We analyze the reconstructed torsion model and find that the torsion field behaves like the quintessence (w>−1) or quintom (exhibiting a transition from w>−1 to w<−1) dark energy, depending on the value of the model parameter c. We then perform a stability analysis according to the squared sound speed. It is shown that the model is classically stable in the current epoch for the case of c<1. We also investigate the model from the viewpoint of statefinder parameters and it turns out that the statefinder trajectories in the r−s plane behave differently for the three cases of c and also quite distinct from those of other cosmological models. From the trajectories of the statefinder pair {q,r}, we find that, for all the three cases of c, the universe has a phase transition from deceleration to acceleration, consistently with cosmological observations. In addition, we fit the reconstructed torsion model with the recent Type Ia supernovae (SNe Ia) samples, i.e., the Pantheon sample containing 1048 SNe Ia with the redshift in the range 0.01<z<2.3 and the Pantheon+ sample with 1701 light curves of 1550 distinct SNe Ia in the range 0.001<z<2.26. The analysis results show that the limits on the present fractional energy density of matter Ωm0 are completely compatible with those of the ΛCDM model obtained from the latest Planck mission observations at 68% confidence level. The mean value of c constrained from the Pantheon sample corresponds to the quintom-like scenario (i.e., c<1) and its mean value from the Pantheon+ sample corresponds to the quintessence-like scenario (i.e., c≥1). However, both of the Pantheon and Pantheon+ samples cannot distinguish the quintom-like and quintessence-like scenarios at 68% confidence level.

Cosmic analysis for some parametrized squared speed of sound models in nonzero torsion cosmology

In this paper, we use some squared speed of sound models in the framework of the nonzero torsion theory for flat FRW spacetime. These squared speeds of sound models depend on equation-of-state (EoS) parameter. We discuss the accelerated expansion of the universe through some cosmological parameters like Hubble parameter, deceleration parameter and statefinder parameters. For deceleration parameter, we get some constraints to be fulfilled by model parameters for the sake of accelerated expansion of the universe. The statefinder parameters show the [Formula: see text]CDM limit as well as some consistent behavior for each model. We also check the validity of generalized second law of thermodynamics and thermal equilibrium for each model by taking into account Bekenstein entropy. In terms of EoS parameter having range of quintessence, cosmological constant as well as phantom era, we get consistent results for particular values of model constants.

Torsion cosmology of Poincaré gauge theory and the constraints of its parameters via SNeIa data

Poincarè gauge theory (PGT) is an alternative gravity theory, which bringsthe gravity into the gauge-theoretic framework, where the Lagrangian includes both quadratictorsion and curvature terms. Recently, the cosmologicalmodels with torsion based on this theory, which explained the cosmic acceleration in anew way, have received much attention. Among these PGT cosmological models, the one with only even paritydynamical modes-SNY model, for its realistic meaning, is very attractive.In this paper, we first analyze the past-time cosmic evolution of SNYmodel analytically. And based on these results we fit this model tothe most comprehensive SNeIa data (Union 2) and thus find the best-fit values of modelparameters and initial conditions, whose related χ2 value is consistentwith the one from ΛCMD at the 1σ level. Also by the χ2estimate, we provide certain constraints on these parameters. Using these best-fitvalues for the Union 2 SNeIa dataset, we are able to predict the evolutionof our real universe in late time. From this prediction, we know that the fate of our universe is thatit would expand forever, slowly asymptotically to a halt, which is in accordancewith the earlier works.

ON THE LATE-TIME EVOLUTION IN A TORSION COSMOLOGY

In this paper, we study the late-time behavior of a torsion cosmology. We show that there is the late-time de Sitter attractor when the torsion parameter a1belongs to [Formula: see text], which indicates the late-time behaviors of torsion cosmology insensitive to the initial condition and thus alleviates the fine-tuning problem. Furthermore, we discuss the evolution of statefinder parameters for torsion cosmology in the four different ranges of a1, and find their typical characteristic different from the other cosmological models. Most of importance, we obtain three kinds of solutions with a constant affine scalar curvature and a kind of expression with the non-constant curvature. Using these expressions, we shall be able to predict the evolution over the late-time in torsion cosmology.

Analytical approach of late-time evolution in a torsion cosmology

In this Letter, we study the late-time evolution of a torsion cosmology only with the spin-0+ mode. We find three kinds of analytical solutions with a constant affine scalar curvature. In the first case, it is not physical because the matter density will be negative. In the second case, it shows that the dark energy can be mimicked in the torsion cosmological model. In the third case, the characteristic of late-time evolution is similar to that of the universe of matter dominant. And we also find a kind of expression with the non-constant curvature that the periodic character of numerical calculation is only the reflection of solution in a specific period of evolution. Using these expressions, we shall be able to predict the evolution over the late-time. From this prediction, we know the fate of universe that the universe would expand forever, slowly asymptotically to a halt.

The torsion cosmology in Kaluza–Klein theory

We have studied the torsion cosmology model in Kaluza–Klein theory. We considered two simple models in which the torsion vectors are Aμ = (α,0,0,0) and Aμ = a(t)2(0,β,β,β), respectively. For the first model, the accelerating expansion of the Universe can be not explained without dark energy which is similar to that in the standard cosmology. But for the second model, we find that without dark energy the effect of torsion can give rise to the accelerating expansion of the universe and the alleviation of the well-known age problem of the three old objects for appropriated value of the model parameter β. These outstanding features of the second torsion cosmology model have been supported by the Type Ia supernovae (SNIa) data.

Statefinder diagnostic in a torsion cosmology

We apply the statefinder diagnostic to the torsion cosmology, inwhich an accounting for the accelerated universe is considered interm of a Riemann-Cartan geometry: dynamic scalar torsion. We findthat there are some typical characteristic of the evolution ofstatefinder parameters for the torsion cosmology that can bedistinguished from the other cosmological models. Furthermore, wealso show that statefinder diagnostic has a direct bearing on thecritical points. The statefinder diagnostic divides the torsionparameter a1 into differential ranges, which is in keeping withthe requirement of dynamical analysis. In addition, we fit thescalar torsion model to ESSENCE supernovae data and give the bestfit values of the model parameters.

Torsion cosmological dynamics

In this paper, the dynamical attractor and heteroclinic orbit have been employed to make the late-time behaviors of the model insensitive to the initial condition and thus alleviate the fine-tuning problem in the torsion cosmology. The late-time de Sitter attractor indicates that torsion cosmology is an elegant scheme and the scalar torsion mode is an interesting geometric quantity for physics. The numerical solutions obtained by Nester et al. are not periodic solutions, but are quasi-periodic solutions near the focus for the coupled nonlinear equations.

Torsion cosmology and the accelerating universe

Investigations of the dynamic modes of the Poincar\'e gauge theory of gravity found only two good propagating torsion modes; they are effectively a scalar and a pseudoscalar. Cosmology affords a natural situation where one might see observational effects of these modes. Here, we consider only the ``scalar torsion'' mode. This mode has certain distinctive and interesting qualities. In particular, this type of torsion does not interact directly with any known matter, and it allows a critical nonzero value for the affine scalar curvature. Via numerical evolution of the coupled nonlinear equations we show that this mode can contribute an oscillating aspect to the expansion rate of the Universe. From the examination of specific cases of the parameters and initial conditions we show that for suitable ranges of the parameters the dynamic ``scalar torsion'' model can display features similar to those of the presently observed accelerating universe.