Probing noncommutativity with inflationary gravitational waves

Cai, Yi-Fu; Piao, Yun-Song

doi:10.1016/j.physletb.2007.09.068

Cited by 37 publications

(40 citation statements)

References 77 publications

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“…(2.13) is valid for α/k 0 ≪ 2/5, since the largest CMB scale is ℓ = 2. This condition is also compatible with a bound evaluated from a constraint on today's graviton mass, namely α 0.01 Mpc −1 [21].…”

Section: Signatures In the Cmb Anisotropiessupporting

confidence: 69%

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CMB statistical anisotropy from noncommutative gravitational waves

Shiraishi

Mota

Ricciardone

et al. 2014

J. Cosmol. Astropart. Phys.

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Abstract. Primordial statistical anisotropy is a key indicator to investigate early Universe models and has been probed by the cosmic microwave background (CMB) anisotropies. In this paper, we examine tensor-mode CMB fluctuations generated from anisotropic gravitational waves, parametrised byis the usual scale-invariant power spectrum. Such anisotropic tensor fluctuations may arise from an inflationary model with noncommutativity of fields. It is verified that in this model, an isotropic component and a quadrupole asymmetry with f 0 (k) = f 2 (k) ∝ k −2 are created and hence highly red-tilted off-diagonal components arise in the CMB power spectra, namely ℓ 2 = ℓ 1 ± 2 in T T , T E, EE and BB, and ℓ 2 = ℓ 1 ± 1 in T B and EB. We find that B-mode polarisation is more sensitive to such signals than temperature and E-mode polarisation due to the smallness of large-scale cosmic variance and we can potentially measure g 00 = 30 and g 2M = 58 at 68% CL in a cosmic-variance-limited experiment. Such a level of signal may be measured in a PRISM like experiment, while the instrumental noise contaminates it in the Planck experiment. These results imply that it is impossible to measure the noncommutative parameter if it is small enough for the perturbative treatment to be valid. Our formalism and methodology for dealing with the CMB tensor statistical anisotropy are general and straightforwardly applicable to other early Universe models.

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Section: Signatures In the Cmb Anisotropiessupporting

confidence: 69%

“…The present case imposes the noncommutativity between conjugate momenta (2.2). This noncommutative effect may be interpreted as an additional term breaking the Lorentz invariance in an effective action [21]:…”

Section: Quantizationmentioning

confidence: 99%

CMB statistical anisotropy from noncommutative gravitational waves

Shiraishi

Mota

Ricciardone

et al. 2014

J. Cosmol. Astropart. Phys.

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“…where ω R and ω L represent the frequency of the Right-handed and Left-handed mode respectively and the subscripts "i" and "f" denotes the initial and final moment of the propagation. Note that due to this rotation, the spectrum of tensor perturbations would be expected to be suppressed at high energy scales, as was shown in a different context in [62].…”

Section: Tensor Perturbationsmentioning

confidence: 55%

Perturbative instabilities in Hořava gravity

Bogdanos

Saridakis

2010

Class. Quantum Grav.

165

146

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We investigate the scalar and tensor perturbations in Hořava gravity, with and without detailed balance, around a flat background. Once both types of perturbations are taken into account, it is revealed that the theory is plagued by ghost-like scalar instabilities in the range of parameters which would render it power-counting renormalizable, that cannot be overcome by simple tricks such as analytic continuation. Implementing a consistent flow between the UV and IR limits seems thus more challenging than initially presumed, regardless of whether the theory approaches General Relativity at low energies or not. Even in the phenomenologically viable parameter space, the tensor sector leads to additional potential problems, such as fine-tunings and super-luminal propagation.

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“…However, there may be more qualitative effects due to transPlanckian physics. For example, polarization of primordial gravitational waves could be an important smoking gun of trans-Planckian physics [6,7,8]. In fact, a parity violating gravitational Chern-Simons term which is ubiquitous in string theory can generate circular polarization in primordial gravitational waves [9,10,11].…”

Section: Introductionmentioning

confidence: 99%

Chiral Primordial Gravitational Waves from a Lifshitz Point

2009

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We study primordial gravitational waves produced during inflation in quantum gravity at a Lifshitz point proposed by Hořava. Assuming power-counting renormalizability, foliation preserving diffeomorphism invariance, and the condition of detailed balance, we show that primordial gravitational waves are circularly polarized due to parity violation. The chirality of primordial gravitational waves is a quite robust prediction of quantum gravity at a Lifshitz point which can be tested through observations of cosmic microwave background radiation and stochastic gravitational waves.

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Probing noncommutativity with inflationary gravitational waves

Cited by 37 publications

References 77 publications

CMB statistical anisotropy from noncommutative gravitational waves

CMB statistical anisotropy from noncommutative gravitational waves

Perturbative instabilities in Hořava gravity

Chiral Primordial Gravitational Waves from a Lifshitz Point

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