Dynamics of cosmological scalar fields

Tamanini, Nicola

doi:10.1103/physrevd.89.083521

Cited by 43 publications

(58 citation statements)

References 69 publications

(108 reference statements)

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“…Furthermore from the constraints 0 ≤ Ω φ ≤ 1, y ≥ 0, the variables (x, y) are bounded in the ranges x ∈ [−1, 1], y ∈ [0, 1] from which follows that that the points (x, y) belong to a half disk; however for the parameter λ there is no constraint that implies that λ ∈ R [45,49]. Furthermore, we consider w m ∈ (−1, 1).…”

Section: Dynamical Analysismentioning

confidence: 99%

Dynamical analysis in scalar field cosmology

et al. 2015

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We give a general method to find exact cosmological solutions for scalar-field dark energy in the presence of perfect fluids. We use the existence of invariant transformations for the Wheeler De Witt (WdW) equation. We show that the existence of a point transformation under which the WdW equation is invariant is equivalent to the existence of conservation laws for the field equations, which indicates the existence of analytical solutions. We extend previous work by providing exact solutions for the Hubble parameter and the effective dark-energy equation of state parameter for cosmologies containing a combination of perfect fluid and a scalar field whose self-interaction potential is a power of hyperbolic functions. We find solutions explicity when the perfect fluid is radiation or cold dark matter and determine the effects of non-zero spatial curvature. Using the Planck 2015 data, we determine the evolution of the effective equation of state of the dark energy. Finally, we study the global dynamics using dimensionless variables. We find that if the current cosmological model is Liouville integrable (admits conservation laws) then there is a unique stable point which describes the de-Sitter phase of the universe.PACS numbers: 98.80.-k, 95.35.+d, 95.36.+x

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Section: Dynamical Analysismentioning

confidence: 99%

Dynamical analysis in scalar field cosmology

et al. 2015

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“…This can be achieved by adding to the matter sector a canonical scalar field [10][11][12][13][14][15][16][17][18][19][20][21][22][23], known as quintessence, a phantom scalar field [24][25][26][27][28][29], or a combination of both of these fields called quintom [30][31][32][33][34][35][36][37][38][39]. A review of these models can be found in [40,41].…”

Section: Introductionmentioning

confidence: 99%

Teleparallel quintessence with a nonminimal coupling to a boundary term

Bahamonde

Wright

2015

Phys. Rev. D

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We propose a new model in the teleparallel framework where we consider a scalar field nonminimally coupled to both the torsion T and a boundary term given by the divergence of the torsion vector B ¼ 2 e ∂ μ ðeT μ Þ. This is inspired by the relation R ¼ −T þ B between the Ricci scalar of general relativity and the torsion of teleparallel gravity. This theory in suitable limits incorporates both the nonminimal coupling of a scalar field to torsion, and the nonminimal coupling of a scalar field to the Ricci scalar. We analyze the cosmology of such models, and we perform a dynamical systems analysis on the case when we have only a pure coupling to the boundary term. It is found that the system generically evolves to a late time accelerating attractor solution without requiring any fine-tuning of the parameters. A dynamical crossing of the phantom barrier is also shown to be possible.

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“…We note here that as obtained in Ref. 35 for the square kinetic correction model we shall consider the case where γ > 0 as it is physically viable (i.e. the adiabatic sound speed is positive).…”

Section: Non-canonical Scalar Field Model and Basic Cosmological Equamentioning

confidence: 95%

“…Further, if one assumes n > 1 2 and γ ≥ 0, then for the present kinetic correction model, the scalar field energy density and speed of sound are both positive, therefore physically viable. 35 Hence, the case of n = 1 2 being the limiting case is of particular interest. For higher-order corrections (n > 2), the corresponding background cosmological equations are very complicated and the analysis is almost impossible to handle even by numerical techniques.…”

Section: Non-canonical Scalar Field Model and Basic Cosmological Equamentioning

confidence: 99%

Thermodynamics of scalar field models with kinetic corrections

Chetry

Dutta

Khyllep

2019

Int. J. Mod. Phys. D

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In the present work, we compare the thermodynamical viability of two types of noncanonical scalar field models with kinetic corrections: the square kinetic and square root kinetic corrections. In modern cosmology, the generalised second law of thermodynamics (GSLT) plays an important role in deciding thermodynamical compliance of a model as one cannot consider a model to be viable if it fails to respect GSLT. Hence, for comparing thermodynamical viability, we examine the validity of GSLT for these two models. For this purpose, by employing the Unified first law (UFL), we calculate the total entropy of these two models in apparent and event horizons. The validity of GSLT is then examined from the autonomous systems as the original expressions of total entropy are very complicated. Although, at the background level, both models give interesting cosmological dynamics, however, thermodynamically we found that the square kinetic correction is more realistic as compared to the square root kinetic correction. More precisely, the GSLT holds for the square kinetic correction throughout the evolutionary history except only during the radiation epoch where the scalar field may not represent a true description of the matter content. On the other hand, the square root kinetic model fails to satisfy the GSLT in major cosmological eras.

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Dynamics of cosmological scalar fields

Cited by 43 publications

References 69 publications

Dynamical analysis in scalar field cosmology

Dynamical analysis in scalar field cosmology

Teleparallel quintessence with a nonminimal coupling to a boundary term

Thermodynamics of scalar field models with kinetic corrections

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