Classification of the FRW universe with a cosmological constant and a perfect fluid of the equation of state p = w ρ

Ha, Te; Huang, Yongqing; Ma, Qianyu; Pechan, Kristen; Renner, Timothy; Wu, Z.; Benesh, Gregory A.; Wang, Anzhong

doi:10.1007/s10714-012-1348-1

Cited by 11 publications

(5 citation statements)

References 60 publications

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“…Since the energy densities of these effective matter components depend on coupling constants in the theory, null energy condition can be violated if the values of coupling constants are arbitrary. As a result, we can find bouncing universe and oscillating universe as singularity-free solutions [12][13][14].…”

Section: Introductionmentioning

confidence: 89%

Stability of singularity-free cosmological solutions in Hořava-Lifshitz gravity

2017

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We study stability of singularity-free cosmological solutions with positive cosmological constant based on projectable Hořava-Lifshitz (HL) theory. In HL theory, the isotropic and homogeneous cosmological solutions with bounce can be realized if spacial curvature is non-zero. By performing perturbation analysis around non-flat Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime, we derive a quadratic action and discuss the stability, i.e, ghost and tachyon-free conditions. Although the squared effective mass of scalar perturbation must be negative in infrared regime, we can avoid tachyon instability by considering strong Hubble friction. Additionally, we estimate the backreaction from the perturbations on background geometry, especially, against anisotropic perturbation in closed FLRW spacetime. It turns out that certain types of bouncing solution may be spoiled even if all perturbation modes are stable.PACS numbers: 98.80.Cq

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Section: Introductionmentioning

confidence: 89%

Stability of singularity-free cosmological solutions in Hořava-Lifshitz gravity

2017

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“…have been extensively analysed, ranging from formal developments (Appignani et al 1999;Afshordi 2009;Blas et al 2009;Cai et al 2009a,b;Calcagni 2009a;Charmousis et al 2009;Germani et al 2009;Hořava 2009a;Iengo et al 2009;Kluson 2009;Kobakhidze 2009;Kocharyan 2009;Li & Pang 2009;Mukohyama 2009a;Nishioka 2009;Orlando & Reffert 2009;Sotiriou et al 2009a,b;Visser 2009;Chen & Huang 2010;Kluson 2010), cosmology (Boehmer & Lobo 2009;Brandenberger 2009;Cai & Saridakis 2009;Calcagni 2009b;Gao 2009;Gao et al 2009;Ha et al 2009;Kalyana Rama 2009;Kiritsis & Kofinas 2009;Kobayashi et al 2009;Minamitsuji 2009;Mukohyama 2009b;Mukohyama et al 2009;Nojiri & Odintsov 2009;Piao 2009;Takahashi & Soda 2009;Wang & Maartens 2009;, dark energy (Park 2009a;Saridakis 2009) and dark matter (Mukohyama 2009c), spherically symmetric or rotating solutions (Botta-Cantcheff et al 2009;Cai et al 2009c,d;…”

Section: Introductionmentioning

confidence: 99%

Solar System tests of Hořava–Lifshitz gravity

2010

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In the present paper, we consider the possibility of observationally constraining Hořava gravity at the scale of the Solar System, by considering the classical tests of general relativity (perihelion precession of the planet Mercury, deflection of light by the Sun and the radar echo delay) for the spherically symmetric black hole KehagiasSfetsos solution of Hořava-Lifshitz gravity. All these gravitational effects can be fully explained in the framework of the vacuum solution of Hořava gravity. Moreover, the study of the classical general relativistic tests also constrains the free parameter of the solution. From the analysis of the perihelion precession of the planet Mercury, we obtain for the free parameter u of the Kehagias-Sfetsos solution the constraint u ≥ 3.212 × 10 −26 cm −2 , the deflection of light by the Sun gives u ≥ 4.589 × 10 −26 cm −2 , while the radar echo delay observations can be explained if the value of u satisfies the constraint u ≥ 9.179 × 10 −26 cm −2 .

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“…For classical perfect fluids, we have 0 ≤ w ≤ 1. However, when dark energy is also taken into account, the range −1 ≤ w ≤ 1 is assumed (see Refs [14,15]…”

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confidence: 99%

Effective actions for loop quantum cosmology in fourth-order gravity

2021

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Loop quantum cosmology (LQC) is a theory which renders the Big Bang initial singularity into a quantum bounce, by means of short-range repulsive quantum effects at the Planck scale. In this work, we are interested in reproducing the effective Friedmann equation of LQC, by considering a generic f(R, P, Q) theory of gravity, where $$R=g^{\mu \nu }R_{\mu \nu }$$ R = g μ ν R μ ν is the Ricci scalar, $$P=R_{\mu \nu }R^{\mu \nu }$$ P = R μ ν R μ ν , and $$Q=R_{\alpha \beta \mu \nu }R^{\alpha \beta \mu \nu }$$ Q = R α β μ ν R α β μ ν is the Kretschmann scalar. An order reduction technique allows us to work in f(R, P, Q) theories which are perturbatively close to General Relativity, and to deduce a modified Friedmann equation in the reduced theory. Requiring that the modified Friedmann equation mimics the effective Friedmann equation of LQC, we are able to derive several functional forms of f(R, P, Q). We discuss the necessary conditions to obtain viable bouncing cosmologies for the proposed effective actions of f(R, P, Q) theory of gravity.

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Classification of the FRW universe with a cosmological constant and a perfect fluid of the equation of state p = w ρ

Cited by 11 publications

References 60 publications

Stability of singularity-free cosmological solutions in Hořava-Lifshitz gravity

Stability of singularity-free cosmological solutions in Hořava-Lifshitz gravity

Solar System tests of Hořava–Lifshitz gravity

Effective actions for loop quantum cosmology in fourth-order gravity

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