Inflation in general covariant Hořava-Lifshitz gravity without projectability

Zhu, Tao; Huang, Yongqing; Wang, Anzhong

doi:10.1007/jhep01(2013)138

Cited by 29 publications

(15 citation statements)

References 73 publications

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“…[49][50][51][52] for examples. In Hořava-Lifshitz theory of quantum gravity, such excited states can be produced by the contribution of high-order spatial derivative terms in the action of the theory, which also supply a nonlinear dispersion relation for the inflationary perturbations [53][54][55]. We note that such nonlinear dispersion relation can also arise from high-order extension of the effective field theory of inflation [56][57][58][59][60] and phenomenological consideration of achieving a nearly scale-invariant power spectrum [61], for examples.…”

Section: Arxiv:191205145v1 [Gr-qc] 11 Dec 2019mentioning

confidence: 94%

Inflationary Cosmology with Quantum Gravitational Effects and Swampland Conjectures*

Wu¹,

Zhu²

2019

Commun. Theor. Phys.

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Recently proposed two swampland criteria that arising from string theory landscape lead to the important challenge of the realization of single-field inflationary models. Especially one of swampland criteria which implies a large tensor-to-scalar ratio is strongly in tension with recent observational results. In this paper, we explore the possibility if the swampland conjectures could be compatible with single-field inflationary scenarios if the effects due to the quantum theory of gravity are considered. We show that the quantum gravitational effects due to the nonlinear dispersion relation provides significant modifications on the amplitude of both the scalar and tensor perturbation spectra. Such modifications could be either raise or reduce the perturbation spectra depending on the values of the parameters in the nonlinear terms of the dispersion relations. Therefore, these effects can reduce the tensor-to-scalar ratio to a smaller value which helps to relax the tension between the swampland conjecture and observational data.

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Section: Arxiv:191205145v1 [Gr-qc] 11 Dec 2019mentioning

confidence: 94%

Inflationary Cosmology with Quantum Gravitational Effects and Swampland Conjectures*

Wu¹,

Zhu²

2019

Commun. Theor. Phys.

Self Cite

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“…6,7,25 These are likely when general covariance is abandoned. 47 This condition assumes that the gravitational potential can be obtained from a superpotential defined on the three-spatial hypersurfaces t = const, the Newtonian limit would not exist, 34 and a scalar field in UV could not be stable. 12 The projectability condition, which is usually taken into consideration with the balance conditions, assumes that the lapse function in the Arnowitt-Deser-Misner (ADM) decompositions is only time dependent.…”

Section: Horava Lifshitz Gravitymentioning

confidence: 99%

“…Recently, HL gravity without the projectability condition has been introduced. 47 In HL gravity, the general structure of the scalar field action is given by a consistent imposing of the corresponding symmetries. 10,11 However, one can, in the construction of the action, obtain the scalar field as,…”

Section: Horava Lifshitz Gravitymentioning

confidence: 99%

“…Such problems have been discussed in Ref. 47. HL gravity without the projectability condition was proposed to solve these problems.…”

Section: Hl Gravity Without the Projectability Conditionmentioning

confidence: 99%

“…45,46 The latter eliminates spin-0 graviton. In flat FLRW space-time, the coupling constant Λ g vanishes, 47 despite its radiative corrections expected from quantum mechanics. Then at vanishing cosmological constant,…”

Section: Hl Gravity Without the Projectability Conditionmentioning

confidence: 99%

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Friedmann inflation in Horava–Lifshitz gravity with a scalar field

Tawfik

Diab

Dahab

2016

Int. J. Mod. Phys. A

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We study Friedmann inflation in general Horava-Lifshitz (HL) gravity with detailed and nondetailed and also without the projectability conditions. Accordingly, we derive the modifications in the Friedmann equations due to single scalar field potentials describing power-law and minimal-supersymmetrically extended inflation. By implementing four types of the equations-of-state characterizing the cosmic background geometry, the dependence of the tensorial and spectral density fluctuations and their ratio on the inflation field is determined. The latter characterizes the time evolution of the inflation field relative to the Hubble parameter. Furthermore, the ratio of tensorial-to-spectral density fluctuations is calculated in dependence on the spectral index. The resulting slow-roll parameters apparently differ from the ones deduced from the standard General Relativity (Friedmann gravity). We also observe that the tensorial-to-spectral density fluctuations continuously decrease when moving from nondetailed HL gravity, to Friedmann gravity, to HL gravity without the projectability, and to detailed HL gravity. This regular pattern is valid for three types of cosmic equations-of-state and different inflation potential models. The results fit well with the recent Planck observations. Universe. Also, it was assumed that the exponential expansion could eliminate the particle horizon and therefore helps in solving the horizon problem. 23 Furthermore, the inflation scenario gives a solid explanation for flatness and homogeneity of our Universe and evolves quantum fluctuations in classical curvature perturbation, as well. 15,33 It is conjectured that during the inflation era the perturbations started out with a small amplitude and gradually grown. This leads to a structure formation and thus even would explain the large-scale structure of the Universe. While detailed mechanism responsible for inflation is not well known yet, a number of predictions have been confirmed by observations 41,43 and the hypothetical field inflaton 18 is thought as a likely candidate.According to the cosmological equations suggested by the nonrelativistic renormalizable gravity, 10,11 the early Universe gets features that may give an alternative to the inflation. The resulting theory, known as Horava-Lifshitz (HL) gravity would be able to avoid the Big Bang singularity. 11 Quantum corrections to gravity are conjectured to replace this singularity with an exponentially expanding de Sitter phase. 40 Recently, the HL gravity is assumed to introduce possible modifications in the standard General Relativity (GR) gravity, especially in strong gravitational regimes. 19,29 This is accompanied by modifications in the gravity itself making it responsible for the accelerated expansion of the Universe. Therefore, one of the natural implications of HL gravity is on the very early Universe. Furthermore, various modified theories of gravity, which are successfully able to unify different inflationary approaches with the late-time Universe acceleration and recent c...

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FLRW Cosmology with Horava-Lifshitz Gravity: Impacts of Equations of State

Tawfik

Dahab

2017

Int J Theor Phys

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Inspired by Lifshitz theory for quantum critical phenomena in condensed matter, Horava proposed a theory for quantum gravity with an anisotropic scaling in ultraviolet. In Horava-Lifshitz gravity (HLG), we have studied the impacts of six types of equations of state on the evolution of various cosmological parameters such as Hubble parameters and scale factor. From the comparison of the general relativity gravity with the HLG with detailed and without with non-detailed balance conditions, remarkable differences are found. Also, a noticeable dependence of singular and non-singular Big Bang on the equations of state is observed. We conclude that HLG explains various epochs in the early universe and might be able to reproduce the entire cosmic history with and without singular Big Bang. approach benefits from the success of QFT in describing all forces (except gravity so-far) and the standard model of the elementary particles. The scalar field theory, that was proposed by Lifshitz in order to explain the quantum critical phenomena in condensed matter [4], inspired Horava to propose a theory for the quantum gravity with an anisotropic scaling in UV. This new approach is thus known as Horava-Lifshitz gravity (HLG) [5,7,8,9,10,11,12,13,14,15], where the dynamical critical exponent (z) makes the theory non-relativistic.In analogy to critical systems, the UV fixed point has been treated [16]. The HLG approach assures causal dynamical triangulations [17], renormalization group approaches based on asymptotic safety [18,19] and symmetries of GR. This approach was discussed in an extensive amount of literature [20,21,22], where problems such as, internal consistency and compatibility with observations are treated, as well. The new dimensionless coupling λ is assumed to approach unity in the infrared (IR) limit with the argumentation that at the HLG-charactering parameter λ = 1, HLG theory can't be reduced to GR. For the sake of completeness, we mention that this is not always the case for all HLG models [23].Recent astrophysical observations obviously indicate that the universe expands with an accelerating rate, probably due to dark energy [24,25]. Besides inflation, a series of symmetry-breaking phase transitions, where topological defects may have been formed [26], were conjecture to take place. On the other hand, the HLG-type approach [5] proposes that the modification in gravity is responsible for the accelerated expansion of the universe.Furthermore, various modified theories for gravity can be implemented [27,28]. They successfully unify various inflation models with the late-time acceleration and cosmological observations. But when endorsing any proposal about (non)singular Big Bang due to controversial quantum gravity approaches such as generalized uncertainty principle (GUP) and modified dispersion relation (MDR) [29] should be seen as unwarranted claims. the Big Bang singularity is a fundamental problem, which should be tackled by a good quantum gravity theory, such as HLG or even better.The present paper is organiz...

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Inflation in general covariant Hořava-Lifshitz gravity without projectability

Cited by 29 publications

References 73 publications

Inflationary Cosmology with Quantum Gravitational Effects and Swampland Conjectures*

Inflationary Cosmology with Quantum Gravitational Effects and Swampland Conjectures*

Friedmann inflation in Horava–Lifshitz gravity with a scalar field

FLRW Cosmology with Horava-Lifshitz Gravity: Impacts of Equations of State

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