Growth of spherical overdensities in scalar-tensor cosmologies

Abstract

The accelerated expansion of the universe is a rather established fact in cosmology and many different models have been proposed as a viable explanation. Many of these models are based on the standard general relativistic framework of non-interacting fluids or more recently of coupled (interacting) dark energy models, where dark energy (the scalar field) is coupled to the dark matter component giving rise to a fifth-force. An interesting alternative is to couple the scalar field directly to the gravity sector via the Ricci scalar. These models are dubbed non-minimally coupled models and give rise to a time-dependent gravitational constant. In this work we study few models falling into this category and describe how observables depend on the strength of the coupling. We extend recent work on the subject by taking into account also the effects of the perturbations of the scalar field and showing their relative importance on the evolution of the mass function. By working in the framework of the spherical collapse model, we show that perturbations of the scalar field have a limited impact on the growth factor (for small coupling constant) and on the mass function with respect to the case where perturbations are neglected.

13 pages, 9 figures, accepted in MNRAS

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• Observational constraints on quintessence models of dark energy
• Cold dark energy constraints from the abundance of galaxy clusters
• Spherical collapse model in agegraphic dark energy cosmologies
• Spherical collapse in Generalized Dark Matter models
• Equivalence between Scalar-Tensor theories and $f(R)$-gravity: From the action to Cosmological Perturbations
• Global properties of the growth index of matter inhomogeneities in the universe
• Dark sector evolution in Horndeski models
• Global properties of the growth index: mathematical aspects and physical relevance
• Spherical collapse in coupled quintessence with a $\Lambda$CDM background
• Effects of tidal gravitational fields in clustering dark energy models
• Structure formation in clustering DBI dark energy model with constant sound speed
• On the consistency of the expansion with the perturbations
• The growth of DM and DE perturbations in DBI non-canonical scalar field scenario
• Spherical collapse in reconstructed dark energy models
• Structure formation in a non-canonical scalar field model of clustering dark energy