Formalizing Anisotropic Inflation in Modified Gravity

Nojiri, S.; Odintsov, S. D.; Oikonomou, V. K.; Constantini, A.

doi:10.48550/arxiv.2210.16383

Cited by 3 publications

(3 citation statements)

References 53 publications

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“…see recent references in modified gravity. 13,14 It is worth mentioning that in recent article 15 an anisotropic bouncing cosmological solution in higher-derivative non-local gravity was found.…”

Section: Introductionmentioning

confidence: 99%

Nonlocal de Sitter gravity and its exact cosmological solutions

Dimitrijevic

Драгович

Rakic

et al. 2022

J. High Energ. Phys.

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This paper is devoted to a simple nonlocal de Sitter gravity model and its exact vacuum cosmological solutions. In the Einstein-Hilbert action with Λ term, we introduce nonlocality by the following way: $$ R-2\Lambda =\sqrt{R-2\Lambda}\kern1em \sqrt{R-2\Lambda}\to \sqrt{R-2\Lambda}\kern1em F\left(\square \right)\kern1em \sqrt{R-2\Lambda} $$ R − 2 Λ = R − 2 Λ R − 2 Λ → R − 2 Λ F □ R − 2 Λ , where $$ F\left(\square \right)=1+{\sum}_{n=1}^{+\infty}\left({f}_n{\square}^n+{f}_{-n}{\square}^{-n}\right) $$ F □ = 1 + ∑ n = 1 + ∞ f n □ n + f − n □ − n is an analytic function of the d’Alembert-Beltrami operator □ and its inverse □−1. By this way, R and Λ enter with the same form into nonlocal version as they are in the local one, and nonlocal operator F(□) is dimensionless. The corresponding equations of motion for gravitational field gμν are presented. The first step in finding some exact cosmological solutions is solving the equation $$ \square \sqrt{R-2\Lambda}=q\sqrt{R-2\Lambda} $$ □ R − 2 Λ = q R − 2 Λ , where q = ζΛ (ζ ∈ R) is an eigenvalue and $$ \sqrt{R-2\Lambda} $$ R − 2 Λ is an eigenfunction of the operator □. We presented and discussed several exact cosmological solutions for homogeneous and isotropic universe. One of these solutions mimics effects that are usually assigned to dark matter and dark energy. Some other solutions are examples of the nonsingular bounce ones in flat, closed and open universe. There are also singular and cyclic solutions. All these cosmological solutions are a result of nonlocality and do not exist in the local de Sitter case.

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Section: Introductionmentioning

confidence: 99%

Nonlocal de Sitter gravity and its exact cosmological solutions

Dimitrijevic

Драгович

Rakic

et al. 2022

J. High Energ. Phys.

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“…Studying anisotropic inflation is one of current challenging projects, for example see. [13] A 1998 study by two independent research groups demonstrated that the universe is expanding at an accelerating rate [14,15]. This evidence established the existence of dark energy where the equation of state, ω, is less than −1/3 today.…”

Section: Jcap06(2024)057mentioning

confidence: 97%

Inflation and isotropization in quintom cosmology

Tajahmad

2024

J. Cosmol. Astropart. Phys.

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This paper studies inflation and isotropization in the quintom model in the Bianchi-I, Bianchi-III, and Kantowski-Sachs backgrounds. First, we investigate inherent properties and generalize Heusler's proposition. Then by the use of the dynamical system approach, we consider the system in multiplicative and collective modes of potentials. The conclusions of Collins and Hawking and also Burd and Barrow are discussed.

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“…It turns out that anisotropic inflation has been considered seriously by many people, e.g., see Ref. [15] and references therein.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic power-law inflation for models of non-canonical scalar fields non-minimally coupled to a two-form field

Pham,

Nguyen,

et al. 2024

Eur. Phys. J. C

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In this paper, we investigate the validity of the so-called cosmic no-hair conjecture in the framework of anisotropic inflation models of non-canonical scalar fields non-minimally coupled to a two-form field. In particular, we focus on two typical k-inflation and Dirac–Born–Infeld inflation models, in which we find a set of exact anisotropic power-law inflationary solutions. Interestingly, these solutions are shown to be stable and attractive during an inflationary phase using the dynamical system analysis. The obtained results indicate that the non-minimal coupling between the scalar and two-form fields acts as a non-trivial source of generating stable spatial anisotropies during the inflationary phase and therefore violates the prediction of the cosmic no-hair conjecture, even when the scalar field is of non-canonical forms. In connection with the Planck 2018 data, tensor-to-scalar ratios of these anisotropic solutions are investigated. As a result, it appears that the tensor-to-scalar ratio of the anisotropic power-law inflationary solution of k-inflation model turns out to be more highly consistent with the Planck 2018 data than that of Dirac-Born-Infeld model.

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Formalizing Anisotropic Inflation in Modified Gravity

Cited by 3 publications

References 53 publications

Nonlocal de Sitter gravity and its exact cosmological solutions

Nonlocal de Sitter gravity and its exact cosmological solutions

Inflation and isotropization in quintom cosmology

Anisotropic power-law inflation for models of non-canonical scalar fields non-minimally coupled to a two-form field

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