A tachyon cosmological model with non-minimal derivative coupling to gravity

Shchigolev, V. K.; Rotova, M. P.

doi:10.1134/s0202289312010161

Cited by 13 publications

(5 citation statements)

References 25 publications

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“…It was also shown that if the kinetic term is coupled to more than one Einstein tensor, then the equation of state is always approximately equal to −1, independently from the potential flatness, and hence the scalar may also be considered a candidate for the inflaton. Tachyon models involving nonminimal derivative coupling have also been explored [45,46], while Chaplygin gas model in this framework were studied in [47]. Moreover, the dynamics of entropy perturbations in the two-field assisted dark energy model with mixed kinetic terms was also studied in [48].…”

Section: Introductionmentioning

confidence: 99%

Cosmological models in modified gravity theories with extended nonminimal derivative couplings

2017

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We construct gravitational modifications that go beyond Horndeski, namely theories with extended nonminimal derivative couplings, in which the coefficient functions depend not only on the scalar field but also on its kinetic energy. Such theories prove to be ghost-free in a cosmological background. We investigate the early-time cosmology and show that a de Sitter inflationary phase can be realized as a pure result of the novel gravitational couplings. Additionally, we study the latetime evolution, where we obtain an effective dark energy sector which arises from the scalar field and its extended couplings to gravity. We extract various cosmological observables and analyse their behavior at small redshifts for three choices of potentials, namely, for the exponential, the powerlaw, and the Higgs potential. We show that the Universe passes from deceleration to acceleration in the recent cosmological past, while the effective dark-energy equation-of-state parameter tends to the cosmological-constant value at present. Finally, the effective dark energy can be phantom-like, although the scalar field is canonical, which is an advantage of the model.PACS numbers: 04.50. Kd, 95.36.+x

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Section: Introductionmentioning

confidence: 99%

Cosmological models in modified gravity theories with extended nonminimal derivative couplings

2017

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“…The simplest class of such scenarios is when the scalar field is non-minimally coupled to gravity, and indeed these "scalar-tensor" theories present very interesting cosmological behavior [41][42][43][44][45][46][47][48]. However, an interesting class of models is obtained if one extends further these constructions by allowing for non-minimal couplings between the curvature and the derivatives of the scalar field [49], which can lead to novel and interesting cosmological features [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68]. Finally, even more complicated extensions can arise considering Galileon and Horndeski theories [69][70][71] or even bi-scalar and multiscalar constructions [72][73][74].…”

Section: Jcap10(2016)021mentioning

confidence: 99%

Hamilton-Jacobi formalism for inflation with non-minimal derivative coupling

Sheikhahmadi

Saridakis

Aghamohammadi

et al. 2016

J. Cosmol. Astropart. Phys.

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Abstract. In inflation with nonminimal derivative coupling there is not a conformal transformation to the Einstein frame where calculations are straightforward, and thus in order to extract inflationary observables one needs to perform a detailed and lengthy perturbation investigation. In this work we bypass this problem by performing a Hamilton-Jacobi analysis, namely rewriting the cosmological equations considering the scalar field to be the time variable. We apply the method to two specific models, namely the power-law and the exponential cases, and for each model we calculate various observables such as the tensor-to-scalar ratio, and the spectral index and its running. We compare them with 2013 and 2015 Planck data, and we show that they are in a very good agreement with observations.

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“…In the scalar tensor theories, a special class of dark energy models is represented by the tachyonic cosmologies, a novel approach originated from string theory [50,51]. The development of tachyonic models has been considered in the past years, leading to various theoretical constructions [52][53][54][55][56][57][58] which can explain the recent accelerated expansion at the large scale structure. In the scalar tensor theories based on general relativity the study of tachyonic fields have been considered in various cosmological applications [59][60][61][62][63].…”

Section: Introductionmentioning

confidence: 99%

Tachyonic cosmology with cubic contractions of the Riemann tensor

Marciu¹

2022

Preprint

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A new cosmological theory is proposed in the theoretical framework of modified gravity theories which is based on a tachyonic field non-minimally coupled with a specific topological invariant constructed with third order contractions of the Riemann tensor. After proposing the action of the cosmological model, the modified Friedmann relations and the Klein-Gordon equations are obtained, describing the corresponding geometrical corrections to the Einstein-Hilbert action. The physical features of the cosmological system are investigated by adopting the dynamical system analysis in the case of an exponential function for the geometrical coupling term. The investigation revealed that the cosmological system can explain the current accelerated expansion of the Universe and the matter dominated epoch, showing a high compatibility to the recent history of our Universe for various values of the coupling coefficients.

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A tachyon cosmological model with non-minimal derivative coupling to gravity

Cited by 13 publications

References 25 publications

Cosmological models in modified gravity theories with extended nonminimal derivative couplings

Cosmological models in modified gravity theories with extended nonminimal derivative couplings

Hamilton-Jacobi formalism for inflation with non-minimal derivative coupling

Tachyonic cosmology with cubic contractions of the Riemann tensor

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