Bouncing Palatini cosmologies and their perturbations

Abstract

Nonsingular cosmologies are investigated in the framework of f(R) gravity within the first order formalism. General conditions for bounces in isotropic and homogeneous cosmology are presented. It is shown that only a quadratic curvature correction is needed to predict a bounce in a flat or to describe cyclic evolution in a curved dust-filled universe. Formalism for perturbations in these models is set up. In the simplest cases, the perturbations diverge at the turnover. Conditions to obtain smooth evolution are derived.

7 pages, 1 figure. v2: added references.

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• Cosmological perturbations in modified teleparallel gravity models
• Palatini formulation of $f(R,T)$ gravity theory, and its cosmological implications
• Palatini formulation of modified gravity with a nonminimal curvature-matter coupling
• Unifying Einstein and Palatini gravities
• Isotropic and Anisotropic Bouncing Cosmologies in Palatini Gravity
• A dynamical system analysis of hybrid metric-Palatini cosmologies
• Inflationary Perturbations in Palatini Generalised Gravity
• The bimetric variational principle for General Relativity
• Big Bounce cosmology for Palatini $R^2$ gravity with a Nieh-Yan term
• Cosmic acceleration from modified gravity with Palatini formalism
• Palatini formulation of the conformally invariant $f\left(R,L_m\right)$ gravity theory
• Non-locality of the C- and D-theories
• Quantum backreaction in evolving FLRW spacetimes
• Anisotropic deformations in a class of projectively-invariant metric-affine theories of gravity
• Cosmological constraints of Palatini $f(\mathcal{R})$ gravity
• Phase transitions during Cyclic-Inflation and Non-gaussianity
• New metric-affine generalizations of gravitational wave geometries
• Perturbations in Bouncing and Cyclic Models, a General Study
• A class of simple bouncing and late-time accelerating cosmologies in f(R) gravity
• Novel aspects of C-theories in Cosmology
• Numerically Investigating the Emergent Cyclic Inflation Scenario
• Before the Bang
• Non-singular Universes a la Palatini