Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity

Abstract

A scalar-tensor theory of gravity can be made not only to account for the current cosmic acceleration, but also to satisfy solar-system and laboratory constraints, by introducing a non-linear derivative interaction for the scalar field. Such an additional scalar degree of freedom is called "Galileon". The basic idea is inspired by the DGP braneworld, but one can construct a ghost-free model that admits a self-accelerating solution. We perform a fully relativistic analysis of linear perturbations in Galileon cosmology. Although the Galileon model can mimic the background evolution of standard $\Lambda$CDM cosmology, the behavior of perturbation is quite different. It is shown that there exists a super-horizon growing mode in the metric and Galileon perturbations at early times, suggesting that the background is unstable. A fine-tuning of the initial condition for the Galileon fluctuation is thus required in order to promote a desirable evolution of perturbations at early times. Assuming the safe initial condition, we then compute the late-time evolution of perturbations and discuss observational implications in Galileon cosmology. In particular, we find anticorrelations in the cross-correlation of the integrated Sachs-Wolfe effect and large scale structure, similar to the normal branch of the DGP model.

15 pages, 11 figures; v2: References added, typos corrected

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• A systematic approach to generalisations of General Relativity and their cosmological implications
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• Effective gravitational couplings for cosmological perturbations in the most general scalar-tensor theories with second-order field equations
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• Inflation and primordial non-Gaussianities of "generalized Galileons"
• Galileons from Lovelock actions
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• Matter perturbations in Galileon cosmology
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• Modified gravity a la Galileon: Late time cosmic acceleration and observational constraints
• Primordial non-Gaussianities in general modified gravitational models of inflation
• Linear perturbations in Galileon gravity models
• Cosmic expansion and growth histories in Galileon scalar-tensor models of dark energy
• Dynamical analysis of generalized Galileon cosmology
• Constraints on Shift-Symmetric Scalar-Tensor Theories with a Vainshtein Mechanism from Bounds on the Time Variation of G
• Selected topics in scalar-tensor theories and beyond
• de Sitter Galileon
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• Generalizing Galileons
• Primordial non-Gaussianity from G-inflation
• Generalized Brans-Dicke theories
• Revisiting fifth forces in the Galileon model
• The parameter space in Galileon gravity models
• Cosmology of the proxy theory to massive gravity
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• Large Scale Structures in Kinetic Gravity Braiding Model That Can Be Unbraided
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• Potential-driven Galileon inflation
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• Cosmology of the selfaccelerating third order Galileon
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• Conserved cosmological perturbation in Galileon models
• Observational Constraints on Kinetic Gravity Braiding from the Integrated Sachs-Wolfe Effect
• Chaotic inflation in modified gravitational theories
• Experimental constraints on the uncoupled Galileon model from SNLS3 data and other cosmological probes
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• Galileon accretion
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• Suppressed cosmic growth in coupled vector-tensor theories
• Bounce and cyclic cosmology in weakly broken galileon theories
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• Quantum corrections for the cubic Galileon in the covariant language
• Scalar-Tensor Gravity and DESI 2024 BAO data
• Weak lensing probe of cubic Galileon model
• Observed galaxy power spectrum in cubic Galileon model
• Evading the theoretical no-go theorem for nonsingular bounces in Horndeski/Galileon cosmology
• On the Trispectrum of Galileon Inflation
• The Music of the Aetherwave - B-mode Polarization in Einstein-Aether Theory
• A new approach to cosmological perturbations in f(R) models
• Bounds from ISW-galaxy cross-correlations on generalized covariant Galileon models
• Galileon intermediate inflation
• Testing gravity with halo density profiles observed through gravitational lensing
• A study on Cubic Galileon Gravity Using N-body Simulations
• Cosmological effects of the Galileon term in Scalar-Tensor Theories
• Chaotic Inflation and Reheating in Generalized Scalar-Tensor Gravity
• Primordial Black Holes Dark Matter and Secondary Gravitational Waves from Warm Higgs-G Inflation
• Brans-Dicke Galileon and the Variational Principle
• First and second order cosmological perturbations in light mass Galileon models
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• Consistency Relation and Non-Gaussianity in a Galileon Inflation