Cosmology in a higher-curvature gravity

Ezawa, Yasuo; Iwasaki, H.; Ohmori, Miki; S.Ueda,; Yamada, Norifumi L.; Yano, Tadashi

doi:10.1088/0264-9381/20/22/016

Cited by 4 publications

(3 citation statements)

References 24 publications

(24 reference statements)

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“…In Section IV we turn to a Hamiltonian formulation "à la Ostrogradsky," taking the trace of the extrinsic curvature as the extra degree of freedom. We believe our treatment is simpler than those presented in [12,13,14,15,16].…”

Section: Introductionmentioning

confidence: 92%

Various Hamiltonian formulations off(R)gravity and their canonical relationships

2009

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Various Hamiltonian formulations of f (R) gravity can be found in the literature. Some authors follow the Ostrogradsky treatment of higher derivative theories and introduce as extra variables first order time derivatives of the metric (typically the extrinsic curvature). Some others take advantage of the conformal equivalence of f (R) theory with Einstein's gravity coupled to a scalar field and introduce as an extra variable the scalar curvature R itself, which includes second time derivatives of the metric. We show that, contrarily to some claims, these formulations are related by canonical transformations.I.

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Section: Introductionmentioning

confidence: 92%

Various Hamiltonian formulations off(R)gravity and their canonical relationships

2009

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“…The latter implies that dξ/dσ ≃ −sgn(σ) 2π 3 sinh(σ) < 0. Several authors have explored special features of the string-derived Lagrangian that might provide some characteristic features of the above model (see for example 7,8,9,10,11,12,13,14,15,16 ).…”

Section: Accelerating Universes and String-inspired Modelsmentioning

confidence: 99%

Constraints on Gauss-Bonnet Cosmologies

Neupane¹

2008

Dark Matter in Astroparticle and Particle Physics

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The modified Gauss-Bonnet gravity can be motivated by a number of physical reasons, including: the uniqueness of a gravitational Lagrangian in four and higher dimensions and the leading order α ′ corrections in superstring theory. Such an effective theory of scalar-tensor gravity has been modeled in the recent past to explain both the initial cosmological singularity problem and the observationally supported cosmological perturbations. Here I present an overview of the recent developments in the use of modified Gauss-Bonnet gravity to explain current observations, touching on key cosmological and astrophysical constraints applicable to theories of scalar-tensor gravity. The Gauss-Bonnet type modifications of Einstein's theory admits nonsingular solutions for a wide range of scalar-curvature couplings. It also provides plausible explanation to some outstanding cosmological conundrums, including: the transition from matter dominance to dark energy and the late time cosmic acceleration. The focus is placed here to constrain such an effective theory of gravity against the recent cosmological and astrophysical observations.

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“…An approach to investigating this issue is to examine theoretical frameworks based on higher dimensions, i.e., beyond our conventional fourdimensional spacetime. In this respect, higher-dimensional gravity theories are taken into account as important ingredients of contemporary theories of fundamental physics, such as Kaluza-Klein, string theory, supergravity [41], as well as holography [42] and cosmological scenarios [43]. Since the advent and development of these ideas, a great deal of effort has been expended to seek out physically reliable alternatives to GR theory.…”

Section: Introductionmentioning

confidence: 99%

Dynamical wormholes in Lovelock gravity

Mehdizadeh,

Ziaie

2021

Preprint

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In this study we present evolving wormhole configurations in third-order Lovelock gravity and investigate the possibility that these solutions satisfy the energy conditions. Using a generalized Friedmann-Robertson-Walker spacetime, we derive evolving wormhole geometries by considering a constraint on the Ricci scalar. In standard cosmological models, the Ricci scalar is independent of the radial coordinate r and is only a function of time. We use this property to introduce dynamic wormhole solutions expanding in an inflationary cosmological background and explore the effects of higher-order Lovelock terms on the dynamics of such wormholes. Our analysis shows that for suitable third-order Lovelock coefficients, there are wormhole solutions that respect the weak energy condition (WEC). In addition to this, we also present other wormhole solutions that satisfy the WEC throughout their respective evolution.

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Cosmology in a higher-curvature gravity

Cited by 4 publications

References 24 publications

Various Hamiltonian formulations off(R)gravity and their canonical relationships

Various Hamiltonian formulations off(R)gravity and their canonical relationships

Constraints on Gauss-Bonnet Cosmologies

Dynamical wormholes in Lovelock gravity

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