Modified gravity away from a ΛCDM background

Brando, Guilherme; Falciano, F. T.; Linder, Eric V.; Velten, Hermano

doi:10.1088/1475-7516/2019/11/018

Cited by 18 publications

(12 citation statements)

References 74 publications

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“…CMB, BAO, SNIa and RSD datasets constrain indeed α M to be negative as shown in Figure 14. Remarkably a negative running of the Planck mass at z 1 does not prevent the model to produce lower growth relative to the standard model nor a positive ISW-galaxy cross-correlation [201].…”

Section: Running Planck Massmentioning

confidence: 89%

“…Pace, G. Papadomanolakis, S. Peirone and D. Vernieri for useful discussions. We acknowledge the authors of [155,131,101,169,79,68,100,158,173,167,186,187,140,195,194,198,201,199,209,106,214,141,216,219,217,168,130,305,306] for the permission to use their figures and we would like to thank also G. Brando…”

Section: Discussionmentioning

confidence: 99%

“…A time dependent DE equation of state allows to explore larger portions of the parameter space. In this case, for example, the running Planck mass can even assume negative values [201]. CMB, BAO, SNIa and RSD datasets constrain indeed α M to be negative as shown in Figure 14.…”

Section: Running Planck Massmentioning

confidence: 94%

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Effective field theory of dark energy: A review

2020

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The discovery of cosmic acceleration has triggered a consistent body of theoretical work aimed at modeling its phenomenology and understanding its fundamental physical nature. In recent years, a powerful formalism that accomplishes both these goals has been developed, the so-called effective field theory of dark energy. It can capture the behavior of a wide class of modified gravity theories and classify them according to the imprints they leave on the smooth background expansion history of the Universe and on the evolution of linear perturbations. The effective field theory of dark energy is based on a Lagrangian description of cosmological perturbations which depends on a number of functions of time, some of which are non-minimal couplings representing genuine deviations from standard gravity. Such a formalism is thus particularly convenient to fit and interpret the wealth of new data that will be provided by future galaxy surveys. Despite its recent appearance, this formalism has already allowed a systematic investigation of what lies beyond the standard gravity landscape and provided a conspicuous amount of theoretical predictions and observational results. In this review, we report on these achievements. Conclusion and outlook 94Appendix A Acronyms and symbols 971. Scalar-tensor theoriesà la Brans-Dicke, hereafter dubbed Generalized

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Section: Running Planck Massmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

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Effective field theory of dark energy: A review

2020

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“…Now we turn to the scalar-tensor theory (1.1), and similarly ask for what values of the EFT couplings is there an obstruction to resummation in the classical theory or to UV completion in the quantum theory? Scalar-tensor theories in this Horndeski class (and its generalisations) form the basis of recent model-independent parameterised approaches that systematically explore modified gravity effects in linear cosmology [20][21][22][23][119][120][121][122][123][124][125][126], resulting in various cosmological constraints on deviations from GR [23,[127][128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144][145][146]. (1.1) is also the theory previously studied in [92,93] and has the convenient feature that positivity bounds can be mapped directly onto constraints on the effective parameters which control linearised cosmological perturbations [23].…”

Section: Horndeski Theoriesmentioning

confidence: 99%

Scalar Fields Near Compact Objects: Resummation versus UV Completion

Davis,

Melville

2021

Preprint

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Low-energy effective field theories containing a light scalar field are used extensively in cosmology, but often there is a tension between embedding such theories in a healthy UV completion and achieving a phenomenologically viable screening mechanism in the IR. Here, we identify the range of interaction couplings which allow for a smooth resummation of classical non-linearities (necessary for kinetic/Vainshtein-type screening), and compare this with the range allowed by unitarity, causality and locality in the underlying UV theory. The latter region is identified using positivity bounds on the 2 Ñ 2 scattering amplitude, and in particular by considering scattering about a non-trivial background for the scalar we are able to place constraints on interactions at all orders in the field (beyond quartic order). We identify two classes of theories can both exhibit screening and satisfy existing positivity bounds, namely scalar-tensor theories of P pXq or quartic Horndeski type in which the leading interaction contains an odd power of X. Finally, for the quartic DBI Galileon (equivalent to a disformally coupled scalar in the Einstein frame), the analogous resummation can be performed near two-body systems and imposing positivity constraints introduces a nonperturbative ambiguity in the screened scalar profile. These results will guide future searches for UV complete models which exhibit screening of fifth forces in the IR.

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“…It is therefore of interest to understand if the hints for MG we found above are driven by such feature. The MGCLASS code allows to manually impose Σ(k, z) = 1, reducing the free MG parameters to only those determining µ(k, z) [78] and obtaining the third function as…”

Section: Assuming No Lensing Deviationmentioning

confidence: 99%

Cosmological Constraints on sub-horizon scales modified gravity theories with MGCLASS II

Sakr,

Martinelli

2021

Preprint

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In this paper we introduce a new public Einstein-Boltzmann solver, MGCLASS II, built as a modification to the publicly available CLASS code, that allows to obtain cosmological observables for Modified Gravity theories. It implements several commonly used parameterizations of deviations from General Relativity, computing their impact on the growth of structure as well as on the background evolution of the Universe, together with a subset of available alternative theories, still not completely ruled out by observations. MGCLASS II is built in such a way to be compatible with parameter estimation codes such as MontePython and Cobaya. We exploit this possibility to constrain the parameterizations used by the Planck collaboration, in order to validate the predictions of this new code, and a newly implemented parameterization (z_flex) which has different features. For the former we find good agreement with the results existing in the literature, while we present original constraints on the parameters of the latter, finding no significant deviation from the standard cosmological model, ΛCDM.

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Modified gravity away from a ΛCDM background

Cited by 18 publications

References 74 publications

Effective field theory of dark energy: A review

Effective field theory of dark energy: A review

Scalar Fields Near Compact Objects: Resummation versus UV Completion

Cosmological Constraints on sub-horizon scales modified gravity theories with MGCLASS II

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