Propagation of gravitational waves in Chern-Simons axion Einstein gravity

Nojiri, Shin’ichi; Odintsov, Sergei D.; Oikonomou, V. K.; Popov, Arkady A.

doi:10.1103/physrevd.100.084009

Cited by 63 publications

(46 citation statements)

References 56 publications

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“…As was shown in [114], the axion field can affect the maximum allowed mass for the neutron star. In addition, in [18], it was shown that the axion field causes inequivalent propagation in the circularly polarized gravitational wave modes. Both the neutron star and gravity waves issues are timely, and perhaps should be further be studied in the axion perspective.…”

Section: Brief Discussion On Future Perspectives: Neutron Stars mentioning

confidence: 99%

“…The non-trivial polarization of gravitational waves in theories involving Chern-Simons axionic couplings is also discussed in the literature [72]. For an important stream of paper on Chern-Simons coupling terms see [18,72,[75][76][77][78][79][80][81][82][83][84][85][86][87]. Moreover, the axions can be related with the H 0 -tension problem [88].…”

Section: Introductionmentioning

confidence: 99%

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Aspects of axion F(R) gravity

Odintsov

Oikonomou

2020

EPL

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We provide a compact review on recent developments on axion F (R) gravity. The axion field is a string theory originating theoretical particle that is a perfect candidate for low-mass particle dark matter. In this review we present how a viable inflationary phenomenology and a viable latetime evolution can be described by an axion F (R) gravity theory, in which the F (R) gravity part can drive in a geometric way the inflationary and the late-time era, and the axion field behaves as dark matter, with its energy density ρa behaving as a function of the scale factor as ρa ∼ a −3 . We also briefly discuss the effect of a non-trivial axion Chern-Simons coupling on the inflationary phenomenology of the R 2 model. Finally, we briefly discuss the effects of a non-minimal coupling of the axion field with the curvature on neutron stars, and also the propagation of gravity waves in Chern-Simons axion gravity.PACS numbers: 04.50. Kd, 95.36.+x, 98.80.Cq,

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Section: Brief Discussion On Future Perspectives: Neutron Stars mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Aspects of axion F(R) gravity

Odintsov

Oikonomou

2020

EPL

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“…Our aim is to solve numerically the differential equation (33) in the redshift interval z ¼ ½0; 10, by using appropriate physical motivated initial conditions which correspond to the late stages of the matter domination era. These are…”

Section: Early and Late Dark Energy Erasmentioning

confidence: 99%

Unifying inflation with early and late dark energy epochs in axion F(R) gravity

Oikonomou

2021

Phys. Rev. D

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121

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We provide a theoretical model of FðRÞ gravity in which it is possible to describe in a unified way inflation, an early and a late dark energy era, in the presence of a light axion particle which plays the role of the dark matter component of the Universe. Particularly, the early time phenomenology is dominated by an R 2 term, while the presence of the other terms fðRÞ ensure the occurrence of the early and late-time dark energy eras. The inflationary phenomenology is compatible with the Planck 2018 data for inflation, while the late-time dark energy era is compatible with the Planck 2018 constraints on the cosmological parameters. Also, the model exhibits an early dark energy era, at z ∼ 2.5 approximately, followed by a deceleration era, which starts at approximately z ∼ 1.5, which in turn is followed by a late-time dark energy era for redshifts z ∼ 0.5, which lasts for approximately 5 billion years up to present time. A notable feature of our model is that the dark energy era is free from dark energy oscillations, at least in the redshift interval z ¼ ½0; 10. In addition, we also discuss several features related to observational data at z ∼ 2.34, at which redshift intricate observational data exist in the literature. Moreover, the numerical code for the dark energy phenomenology, written in PYTHON3, is presented in the end of the article. Finally, the model has another interesting characteristic, a sudden jump of the value of the Hubble rate in the redshift interval z ∼ ½2; 2.6 where its value suddenly increases and then decreases until z ∼ 0.

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“…Compactifications in string theory generically predict the existence of axions in 4-dimensional low-energy effective field theory. The gravitational Chern-Simons coupling commonly arises in the string axiverse as the Chern-Pontryagin density [18,19], which can affect tensor perturbations during their propagation [20][21][22][23][24][25][26][27][28]. Due to the weakness of gravitational interaction, the string corrections are weakly constrained.…”

Section: Introductionmentioning

confidence: 99%

Resonance instability of primordial gravitational waves during inflation in Chern–Simons gravity

Liu

Zhu

et al. 2021

Eur. Phys. J. C

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We investigate axion inflation where the gravitational Chern–Simons term is coupled to a periodic function of the inflaton. We find that tensor perturbations with different polarizations are amplified in different ways by the Chern–Simons coupling. Depending on the model parameters, the resonance amplification results in a parity-violating peak or a board plateau in the energy spectrum of gravitational waves, and the sharp cutoff in the infrared region constitutes a characteristic distinguishable from stochastic gravitational wave backgrounds produced by matter fields in Einstein gravity.

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Propagation of gravitational waves in Chern-Simons axion Einstein gravity

Cited by 63 publications

References 56 publications

Aspects of axion F(R) gravity

Aspects of axion F(R) gravity

Unifying inflation with early and late dark energy epochs in axion F(R) gravity

Resonance instability of primordial gravitational waves during inflation in Chern–Simons gravity

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