Inflation in a renormalizable cosmological model and the cosmic no-hair conjecture

Maeda, Kei Ichi; Stein-Schabes, Jaime A.; Futamase, Toshifumi

doi:10.1103/physrevd.39.2848

Cited by 46 publications

(29 citation statements)

References 38 publications

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“…However, isotropization during inflation occurs in mixed f (φ, R) models (Maeda et al, 1989) In addition to the exact cosmological solutions explored for the purpose of explaining the current cosmic acceleration [see, e.g., (Abdalla et al, 2005;Barrow and Clifton, 2006;Clifton, 2006aClifton, , 2007Clifton andBarrow, 2005b, 2006) and (Capozziello and De Felice, 2008;Capozziello et al, 2007c;Modak et al, 2005;Vakili, 2008) for an approach based on Noether symmetries; see for bouncing solutions and the conditions that they satisfy], exact spherically symmetric solutions of metric f (R) gravity have been explored in the literature, with most recent studies being motivated by the need to understand the weak-field limit of cosmologically-motivated theories.…”

Section: Vacuum and Non-vacuum Exact Solutionsmentioning

confidence: 99%

Metric-affine f(R) theories of gravity

2007

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Modified gravity theories have received increased attention lately due to combined motivation coming from high-energy physics, cosmology and astrophysics. Among numerous alternatives to Einstein's theory of gravity, theories which include higher order curvature invariants, and specifically the particular class of f (R) theories, have a long history. In the last five years there has been a new stimulus for their study, leading to a number of interesting results. We review here f (R) theories of gravity in an attempt to comprehensively present their most important aspects and cover the largest possible portion of the relevant literature. All known formalisms are presentedmetric, Palatini and metric-affine -and the following topics are discussed: motivation; actions, field equations and theoretical aspects; equivalence with other theories; cosmological aspects and constraints; viability criteria; astrophysical applications.

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Section: Vacuum and Non-vacuum Exact Solutionsmentioning

confidence: 99%

Metric-affine f(R) theories of gravity

2007

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“…The field equations from this lagrangian contain terms of fourth-order in the metric with a non-minimally coupled scalar field φ and has been considered in the context of inflationary cosmology by Maeda et al [19]. It can be rewritten by introducing the dynamically equivalent action whose field equations are second-order with respect to the metric with two scalar fields.…”

Section: Examplementioning

confidence: 99%

Extended gravity theories and the Einstein--Hilbert action

Wands

1994

Class. Quantum Grav.

387

337

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I discuss the relation between arbitrarily high-order theories of gravity and scalartensor gravity at the level of the field equations and the action. I show that (2n+4)-order gravity is dynamically equivalent to Brans-Dicke gravity with an interaction potential for the Brans-Dicke field and n further scalar fields. This scalar-tensor action is then conformally equivalent to the Einstein-Hilbert action with n + 1 scalar fields. This clarifies the nature and extent of the conformal equivalence between extended gravity theories and general relativity with many scalar fields. PACS number 04.50

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“…In the early stage of the universe, we may also expect an accelerating expansion of the universe, the so-called inflation [5][6][7][8][9][10][11](For many reviews of inflation see for example [12,13]). Although we do not know the origin of the inflaton field, which is responsible for the accelerating expansion in the early stage of the universe, one possible answer could be modification of a gravitational theory such as Higgs inflation model [14][15][16][17][18][19][20][21][22][23][24]. Although we have not yet had a satisfactory viable explanation to solve inflation as well as dark energy in the framework of modern physics, we recently find an astounding increase in the proposal of modified theories of gravity [25,26].…”

Section: Introductionmentioning

confidence: 99%

Metric-affine gravity and inflation

2019

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We classify the metric-affine theories of gravitation, in which the metric and the connections are treated as independent variables, by use of several constraints on the connections. Assuming the Einstein-Hilbert action, we find that the equations for the distortion tensor (torsion and nonmetricity) become algebraic, which means that those variables are not dynamical. As a result, we can rewrite the basic equations in the form of Riemannian geometry. Although all classified models recover the Einstein gravity in the Palatini formalism (in which we assume there is no coupling between matter and the connections), but when matter field couples to the connections, the effective Einstein equations include an additional hyper energy-momentum tensor obtained from the distortion tensor. Assuming a simple extension of a minimally coupled scalar field in metricaffine gravity, we analyze an inflationary scenario. Even if we adopt a chaotic inflation potential, certain parameters could satisfy observational constraints. Furthermore, we find that a simple form of Galileon scalar field in metric-affine could cause G-inflation.

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Inflation in a renormalizable cosmological model and the cosmic no-hair conjecture

Cited by 46 publications

References 38 publications

Metric-affine f(R) theories of gravity

Metric-affine f(R) theories of gravity

Extended gravity theories and the Einstein--Hilbert action

Metric-affine gravity and inflation

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