Post-Newtonian parameters of ghost-free parity-violating gravities

Qiao, Jin; Zhu, Tao; Li, Guoliang; Zhao, Wen

doi:10.1088/1475-7516/2022/04/054

Cited by 16 publications

(11 citation statements)

References 68 publications

(123 reference statements)

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“…As we have already described in the introduction, some of the parity-violating gravities have been examined by GW observations and give updated constraints on their respective corresponding energy scale M PV . For the ghost-free parity-violating gravity, using the results of the framedragging measurement with the GPB in the Solar System experiment we have given the energy scale constraint: M −1 PV ≲ 10 4 m, which is consistent with the constraint obtained for CS gravity when the same factors are taken into account (Qiao et al, 2022). The latest constraint on M PV is also given using the event data from the GW detection to examine ghost-free parity-violating gravity, which we will describe later.…”

Section: Gravitational Waves In Ghost-free Parity-violating Gravitysupporting

confidence: 72%

Testing parity symmetry of gravity with gravitational waves

Qiao

Zhao

Zhu

et al. 2023

Front. Astron. Space Sci.

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The examination of parity symmetry in gravitational interactions has drawn increasing attention. Although Einstein’s General Relativity is parity-conserved, numerous theories of parity-violating (PV) gravity in different frameworks have recently been proposed for different motivations. In this review, we briefly summarize the recent progress of these theories, and focus on the observable effects of PV terms in the gravitational waves (GWs), which are mainly reflected in the difference between the left-hand and right-hand polarization modes. We are primarily concerned with the implications of these theories for GWs generated by the compact binary coalescences and the primordial GWs generated in the early Universe. The deviation of GW waveforms and/or primordial power spectrum can always be quantified by the energy scale of parity violation of the theory. Applying the current and future GW observation from laser interferometers and cosmic microwave background radiation, the current and potential constraints on the PV energy scales are presented, which indicates that the parity symmetry of gravity can be tested in high energy scale in this new era of gravitational waves.

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Section: Gravitational Waves In Ghost-free Parity-violating Gravitysupporting

confidence: 72%

Testing parity symmetry of gravity with gravitational waves

Qiao

Zhao

Zhu

et al. 2023

Front. Astron. Space Sci.

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“…[12,13] that the NYTG model is ghost-free. Recently, this model was found to be compatible with the results of most local tests in the Solar System at the post-Newtonian order [18,19], the upper limit on its model parameters by the GWs data of LIGO/Virgo Collaboration was obtained in Ref. [20], and the enhancement of primordial GWs during inflation due to the velocity birefringence of NYTG model and its implications in the air-based GWs experiments were studied in Ref.…”

Section: Introductionsupporting

confidence: 55%

Irregular universe in the Nieh-Yan modified teleparallel gravity

Li¹,

Rao²

2023

Preprint

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The Nieh-Yan modified teleparallel gravity is a model which modifies the general relativity equivalent teleparallel gravity by a coupling between the Nieh-Yan density and an axion-like field. This model predicts parity violations in the gravitational waves if the axion-like field has a non-trivial background, and more importantly it is ghost free and avoids the pathologies presented in other parity-violating gravity models. The cosmological dynamics and perturbations of the Nieh-Yan modified teleparallel gravity have been investigated in detail, but all these previous investigations rely on the symmetry requirement that in the background universe both the metric and affine connection are homogeneous and isotropic. In this paper we relax the symmetry constraint on the connection and leave it arbitrary at the beginning, after all the cosmological principle only needs the metric of the background spacetime to meet the symmetry requirement. We find a new flat universe solution for the Nieh-Yan modified teleparallel gravity, for which the background dynamics itself is unchanged but the perturbations around it present a new feature that the scalar and tensor perturbations are coupled together at the linear level. The implications of this peculiar feature in primordial perturbations from inflation are also discussed.

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“…GWs in such Lorentz breaking PV gravity models have been studied in [71][72][73][74][75][76][77][78][79][80][81]. When torsion is turned on, the simplest term that corresponds to the CS term is the so-called Nieh-Yan term [82].…”

Section: Jcap10(2022)054mentioning

confidence: 99%

Circularly polarized scalar induced gravitational waves from the Chern-Simons modified gravity

Zhang

Feng

Gao

2022

J. Cosmol. Astropart. Phys.

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We investigate the scalar induced gravitational waves (SIGWs) in the Chern-Simons (CS) modified gravity during the radiation dominated era. The SIGWs are circularly polarized, which provide us a tool to test the possible parity violation in the early universe. We derive the semianalytic expressions to evaluate the fractional energy density of the SIGWs, ΩGW, which receives contributions from the general relativity (GR) and the correction due to the parity-violating term, respectively. We find that the degree of the circular polarization of the SIGWs can be as large as of order unity, although the contribution to ΩGW from the CS term is at most of the same order as that from the GR.

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Post-Newtonian parameters of ghost-free parity-violating gravities

Cited by 16 publications

References 68 publications

Testing parity symmetry of gravity with gravitational waves

Testing parity symmetry of gravity with gravitational waves

Irregular universe in the Nieh-Yan modified teleparallel gravity

Circularly polarized scalar induced gravitational waves from the Chern-Simons modified gravity

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