Introduction to Palatini Theories of Gravity and Nonsingular Cosmologies

Olmo, Gonzalo J.

doi:10.5772/51807

Cited by 5 publications

(2 citation statements)

References 37 publications

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“…(8) for the cases n = 5/2 and n = 10. We thus conclude that the avoidance of cosmic big bang singularities in Born-Infeld and Born-Infeld like theories [42] is a rather robust phenomenon that does not require fine-tuning in the parameters of the theory, and a generic prediction of Palatini gravities [47]. The smooth recovery of the dynamics of GR at lower curvatures [see the discussion above Eq.…”

Section: Discussionmentioning

confidence: 99%

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Born-Infeld gravity and its functional extensions

2014

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We investigate the dynamics of a family of functional extensions of the (Eddington-inspired) BornInfeld gravity theory, constructed with the inverse of the metric and the Ricci tensor. We provide a generic formal solution for the connection and an Einstein-like representation for the metric field equations of this family of theories. For particular cases we consider applications to the early-time cosmology and find that non-singular universes with a cosmic bounce are very generic and robust solutions.

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Section: Discussionmentioning

confidence: 99%

“…one can verify that the time-time component of the Einstein tensor of the metric t µν leads to [47] 3 H +∆ 2∆ where H =ȧ/a,∆ = d∆/dt, and…”

Section: A Cosmological Modelsmentioning

confidence: 99%

Born-Infeld gravity and its functional extensions

2014

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Cosmophysics of Modified Gravity

Lazkoz

2021

Modified Gravity and Cosmology

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Palatini formulation of f(R, T) gravity theory, and its cosmological implications

Jimin¹,

Li²,

Harkó³

et al. 2018

Eur. Phys. J. C

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We consider the Palatini formulation of f (R, T ) gravity theory, in which a non-minimal coupling between the Ricci scalar and the trace of the energy-momentum tensor is introduced, by considering the metric and the affine connection as independent field variables. The field equations and the equations of motion for massive test particles are derived, and we show that the independent connection can be expressed as the Levi-Civita connection of an auxiliary, energy-momentum trace dependent metric, related to the physical metric by a conformal transformation. Similar to the metric case, the field equations impose the nonconservation of the energy-momentum tensor. We obtain the explicit form of the equations of motion for massive test particles in the case of a perfect fluid, and the expression of the extra force, which is identical to the one obtained in the metric case. The thermodynamic interpretation of the theory is also briefly discussed. We investigate in detail the cosmological implications of the theory, and we obtain the generalized Friedmann equations of the f (R, T ) gravity in the Palatini formulation. Cosmological models with Lagrangians of the type f = R − α 2 /R + g(T ) and f = R + α 2 R 2 + g(T ) are investigated. These models lead to evolution equations whose solutions describe accelerating Universes at late times.

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Introduction to Palatini Theories of Gravity and Nonsingular Cosmologies

Cited by 5 publications

References 37 publications

Born-Infeld gravity and its functional extensions

Born-Infeld gravity and its functional extensions

Cosmophysics of Modified Gravity

Palatini formulation of f(R, T) gravity theory, and its cosmological implications

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