An effective Lagrangian approach, partly inspired by Quantum Loop Cosmology (QLC), is presented and formulated in a non flat FLRW space-times, making use of modified gravitational models. The models considered are non generic, and their choice is dictated by the necessity to have at least second order differential equations of motion in a non flat FLRW space-time. This is accomplished by a class of Lagrangian which are not analytic in the curvature invariants, or making use of a mimetic gravitational scalar field. It is shown that, for some effective models, the associated generalized Friedmann equation, in general, may admit non singular metrics as solutions, while the de Sitter space-time is present only for a restricted class, which includes General Relativity and Lovelock gravity. The other models admit pseudo de Sitter solutions, namely FLRW metrics, such that for vanishing spatial curvature looks like flat de Sitter patch, but for non vanishing spatial curvature are regular bounce metrics or, when the spatial curvature is negative, Big-Bang singular metrics. © 2020 Elsevier B.V. All rights reserved.

Higher derivative and mimetic models on non flat FLRW space-times / Casalino, Alessandro; Sebastiani, Lorenzo; Vanzo, Luciano; Zerbini, Sergio. - In: PHYSICS OF THE DARK UNIVERSE. - ISSN 2212-6864. - 29:(2020), pp. 100594.1-100594.9. [10.1016/j.dark.2020.100594]

Higher derivative and mimetic models on non flat FLRW space-times

Casalino, Alessandro;Sebastiani, Lorenzo;Vanzo, Luciano;Zerbini, Sergio
2020-01-01

Abstract

An effective Lagrangian approach, partly inspired by Quantum Loop Cosmology (QLC), is presented and formulated in a non flat FLRW space-times, making use of modified gravitational models. The models considered are non generic, and their choice is dictated by the necessity to have at least second order differential equations of motion in a non flat FLRW space-time. This is accomplished by a class of Lagrangian which are not analytic in the curvature invariants, or making use of a mimetic gravitational scalar field. It is shown that, for some effective models, the associated generalized Friedmann equation, in general, may admit non singular metrics as solutions, while the de Sitter space-time is present only for a restricted class, which includes General Relativity and Lovelock gravity. The other models admit pseudo de Sitter solutions, namely FLRW metrics, such that for vanishing spatial curvature looks like flat de Sitter patch, but for non vanishing spatial curvature are regular bounce metrics or, when the spatial curvature is negative, Big-Bang singular metrics. © 2020 Elsevier B.V. All rights reserved.
2020
Casalino, Alessandro; Sebastiani, Lorenzo; Vanzo, Luciano; Zerbini, Sergio
Higher derivative and mimetic models on non flat FLRW space-times / Casalino, Alessandro; Sebastiani, Lorenzo; Vanzo, Luciano; Zerbini, Sergio. - In: PHYSICS OF THE DARK UNIVERSE. - ISSN 2212-6864. - 29:(2020), pp. 100594.1-100594.9. [10.1016/j.dark.2020.100594]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/266071
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