Hořava Gravity in the Effective Field Theory formalism: From cosmology to observational constraints

Frusciante, Noemi; Raveri, Marco; Vernieri, Daniele; Hu, Bambi; Silvestri, Alessandra

doi:10.1016/j.dark.2016.03.002

Cited by 55 publications

(86 citation statements)

References 161 publications

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“…[12], while the remaining operators have been introduced by some of the authors of this paper in Ref. [41], where it is shown that they are necessary to map the high-energy Hořava gravity action [71] in the EFT formalism.…”

Section: (1 + ω(T))r + λ(T) − C(t)δgmentioning

confidence: 99%

An extended action for the effective field theory of dark energy: a stability analysis and a complete guide to the mapping at the basis of EFTCAMB

Frusciante

Papadomanolakis

Silvestri

2016

J. Cosmol. Astropart. Phys.

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We present a generalization of the effective field theory (EFT) formalism for dark energy and modified gravity models to include operators with higher order spatial derivatives. This allows the extension of the EFT framework to a wider class of gravity theories such as Hořava gravity. We present the corresponding extended action, both in the EFT and the Arnowitt-Deser-Misner (ADM) formalism, and proceed to work out a convenient mapping between the two, providing a self contained and general procedure to translate a given model of gravity into the EFT language at the basis of the Einstein-Boltzmann solver EFTCAMB. Putting this mapping at work, we illustrate, for several interesting models of dark energy and modified gravity, how to express them in the ADM notation and then map them into the EFT formalism. We also provide for the first time, the full mapping of GLPV models into the EFT framework. We next perform a thorough analysis of the physical stability of the generalized EFT action, in absence of matter components. We work out viability conditions that correspond to the absence of ghosts and modes that propagate with a negative speed of sound in the scalar and tensor sector, as well as the absence of tachyonic modes in the scalar sector. Finally, we extend and generalize the phenomenological basis in terms of α-functions introduced to parametrize Horndeski models, to cover all theories with higher order spatial derivatives included in our extended action. We elaborate on the impact of the additional functions on physical quantities, such as the kinetic term and the speeds of propagation for scalar and tensor modes. Contents

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Section: (1 + ω(T))r + λ(T) − C(t)δgmentioning

confidence: 99%

An extended action for the effective field theory of dark energy: a stability analysis and a complete guide to the mapping at the basis of EFTCAMB

Frusciante

Papadomanolakis

Silvestri

2016

J. Cosmol. Astropart. Phys.

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“…Among cosmologists, it isn't unfamiliar that, in inflationary Universe an ad hoc EoS for dark energy can be ruled out [26,27]. But for late time cosmology where HLG is conjectured to reduce to Einstein's GRG, evidences for dark energy appear.…”

Section: Reminder To Horava-lifshitz Gravitymentioning

confidence: 99%

Minimal-supersymmetric extended inflation field in Horava–Lifshitz gravity

Tawfik¹,

Diab²,

Dahab

2017

Int. J. Mod. Phys. D

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We study the Friedmann inflation in general covariant Horava-Lifshitz (HL) gravity without the projectability conditions and with detailed and non-detailed balance conditions. Accordingly, we derive modifications in the Friedmann equations due to a single-scalar field potential describing minimalsupersymmetrically extended inflation. By implementing two time-independent equations of state (EoS) characterizing the cosmic background geometry filled up with dark energy, the dependence of the tensorial and scalar density fluctuations and their ratios on the inflation field are determined.The latter refer to the time evolution of the inflationary field relative to the Hubble parameter.Furthermore, the ratios of tensorial-to-spectral density fluctuations are calculated in dependence on the spectral index. For cold dark energy EoS ω = −1/3, we find that the tensorial-to-spectral density fluctuations are not depending on the different theories of gravity and the results are very small relative to the recent BICEP2/Keck Array-Planck observations, 10 −9 r 10 −3 . We have also calculated the tensorial and scalar perturbations of the primordial spectra.

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“…The EFT approach preserves a direct link with those theories of modified gravity which show one extra scalar DoF and they can be fully mapped in the EFT language [11][12][13]19,20,26]. Then, by using the mapping with specific theories and the solution in the dS limit for the chosen theories, we can deduce the behavior of the EFT functions.…”

Section: The De Sitter Limitmentioning

confidence: 99%

“…For the present purpose we adopt the action (2), which includes theories like Horndeski/generalized Galileon [31,32], beyond Horndeski (GLPV) [33] and low-energy Hořava gravity [4,34,35]; however, the EFT action has been generalized to include a wider range of theories [20], in particular extensions of Hořava gravity [26,36]. Now, let us use the Arnowitt-Deser-Misner formalism [37] and expand the line element around the flat FLRW background.…”

Section: Modifying General Relativitymentioning

confidence: 99%

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de Sitter limit analysis for dark energy and modified gravity models

2017

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The effective field theory of dark energy and modified gravity is supposed to well describe, at low energies, the behavior of the gravity modifications due to one extra scalar degree of freedom. The usual curvature perturbation is very useful when studying the conditions for the avoidance of ghost instabilities as well as the positivity of the squared speeds of propagation for both the scalar and tensor modes, or the Stückelberg field performs perfectly when investigating the evolution of linear perturbations. We show that the viable parameter space identified by requiring no-ghost instabilities and positive squared speeds of propagation does not change by performing a field redefinition, while the requirement of the avoidance of tachyonic instability might instead be different. Therefore, we find it interesting to associate to the general modified gravity theory described in the effective field theory framework, a perturbation field which will inherit all of the properties of the theory. In the present paper we address the following questions: (1) how can we define such a field? and (2) what is the mass of such a field as the background approaches a final de Sitter state? We define a gauge-invariant quantity which identifies the density of the dark energy perturbation field valid for any background. We derive the mass associated to the gauge-invariant dark energy field on a de Sitter background, which we retain to be still a good approximation also at very low redshift (z ≃ 0). On this background we also investigate the value of the speed of propagation and we find that there exist classes of theories which admit a nonvanishing speed of propagation, even in the Horndeski model, for which a zero speed of sound has previously been found in the literature. We finally apply our results to specific well-known models.

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Hořava Gravity in the Effective Field Theory formalism: From cosmology to observational constraints

Cited by 55 publications

References 161 publications

An extended action for the effective field theory of dark energy: a stability analysis and a complete guide to the mapping at the basis of EFTCAMB

An extended action for the effective field theory of dark energy: a stability analysis and a complete guide to the mapping at the basis of EFTCAMB

Minimal-supersymmetric extended inflation field in Horava–Lifshitz gravity

de Sitter limit analysis for dark energy and modified gravity models

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