A class of effective field theory models of cosmic acceleration

Bloomfield, Jolyon; Flanagan, Éanna É.

doi:10.1088/1475-7516/2012/10/039

Cited by 55 publications

(95 citation statements)

References 77 publications

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“…It has been used to construct general theories of inflation [790,[798][799][800][801][802][803][804] and cosmic acceleration [232,237,[805][806][807][808][809][810]. Additionally black holes have been studied in this theory in [811][812][813][814][815][816][817], and it has been generalized to describe multiple fields non-minimmally coupled to gravity [818][819][820].…”

Section: Horndeski Theorymentioning

confidence: 99%

Beyond the cosmological standard model

et al. 2015

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After a decade and a half of research motivated by the accelerating universe, theory and experiment have a reached a certain level of maturity. The development of theoretical models beyond Λ or smooth dark energy, often called modified gravity, has led to broader insights into a path forward, and a host of observational and experimental tests have been developed. In this review we present the current state of the field and describe a framework for anticipating developments in the next decade. We identify the guiding principles for rigorous and consistent modifications of the standard model, and discuss the prospects for empirical tests.We begin by reviewing recent attempts to consistently modify Einstein gravity in the infrared, focusing on the notion that additional degrees of freedom introduced by the modification must "screen" themselves from local tests of gravity. We categorize screening mechanisms into three broad classes: mechanisms which become active in regions of high Newtonian potential, those in which first derivatives of the field become important, and those for which second derivatives of the field are important. Examples of the first class, such as f (R) gravity, employ the familiar chameleon or symmetron mechanisms, whereas examples of the last class are galileon and massive gravity theories, employing the Vainshtein mechanism. In each case, we describe the theories as effective theories and discuss prospects for completion in a more fundamental theory. We describe experimental tests of each class of theories, summarizing laboratory and solar system tests and describing in some detail astrophysical and cosmological tests. Finally, we discuss prospects for future tests which will be sensitive to different signatures of new physics in the gravitational sector.The review is structured so that those parts that are more relevant to theorists vs. observers/experimentalists are clearly indicated, in the hope that this will serve as a useful reference for both audiences, as well as helping those interested in bridging the gap between them.

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Section: Horndeski Theorymentioning

confidence: 99%

Beyond the cosmological standard model

et al. 2015

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“…In Table I, we count the number and type of derivatives acting on the metric and scalar field perturbations for each of the operators in (9).…”

Section: Choice Of Operatorsmentioning

confidence: 99%

A simplified approach to general scalar-tensor theories

Bloomfield¹

2013

J. Cosmol. Astropart. Phys.

113

163

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The most general covariant action describing gravity coupled to a scalar field with only second order equations of motion, Horndeski's theory (also known as "Generalized Galileons"), provides an all-encompassing model in which single scalar dark energy models may be constrained. However, the generality of the model makes it cumbersome to manipulate. In this paper, we demonstrate that when considering linear perturbations about a Friedmann-Robertson-Walker background, the theory is completely specified by only six functions of time, two of which are constrained by the background evolution. We utilise the ideas of the Effective Field Theory of Inflation/Dark Energy to explicitly construct these six functions of time in terms of the free functions appearing in Horndeski's theory. These results are used to investigate the behavior of the theory in the quasistatic approximation. We find that only four functions of time are required to completely specify the linear behavior of the theory in this limit, which can further be reduced if the background evolution is fixed. This presents a significantly reduced parameter space from the original presentation of Horndeski's theory, giving hope to the possibility of constraining the parameter space. This work provides a cross-check for previous work on linear perturbations in this theory, and also generalizes it to include spatial curvature.

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“…If we consider the n-th order interaction term ϕ n , the corresponding action transforms as 25) where in the last proportionality we used the fact that the energy E scales as E → c −z E. When z = 3, the exponent −(z +3+ns)/z is −2 for any n, so the non-linear interactions are power-counting renormalizable. This power-counting renormalizability also holds for the anisotropic scaling with z > 3.…”

Section: B Hořava-lifshitz Gravitymentioning

confidence: 99%

“…Let us derive the primordial power spectrum of ζ generated during inflation. For this purpose we express ζ in Fourier space, as 25) where τ ≡ a −1 dt is the conformal time, k is the comoving wavenumber, and…”

Section: The Inflationary Power Spectra Of Curvature and Tensor Pementioning

confidence: 99%

Effective field theory approach to modified gravity including Horndeski theory and Hořava–Lifshitz gravity

Kase

Tsujikawa

2014

Int. J. Mod. Phys. D

126

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We review the effective field theory of modified gravity in which the Lagrangian involves three dimensional geometric quantities appearing in the 3+1 decomposition of space-time. On the flat isotropic cosmological background we expand a general action up to second order in the perturbations of geometric scalars, by taking into account spatial derivatives higher than two. Our analysis covers a wide range of gravitational theories-including Horndeski theory/its recent generalizations and the projectable/non-projectable versions of Hořava-Lifshitz gravity. We derive the equations of motion for linear cosmological perturbations and apply them to the calculations of inflationary power spectra as well as the dark energy dynamics in Galileon theories. We also show that our general results conveniently recover stability conditions of Hořava-Lifshitz gravity already derived in the literature.

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A class of effective field theory models of cosmic acceleration

Cited by 55 publications

References 77 publications

Beyond the cosmological standard model

Beyond the cosmological standard model

A simplified approach to general scalar-tensor theories

Effective field theory approach to modified gravity including Horndeski theory and Hořava–Lifshitz gravity

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