Measuring chiral gravitational waves in Chern-Simons gravity with CMB bispectra

Bartolo, N.; Orlando, Giorgio; Shiraishi, Maresuke

doi:10.1088/1475-7516/2019/01/050

Cited by 73 publications

(64 citation statements)

References 47 publications

(80 reference statements)

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“…We stress that there are also other theoretical models that yield interesting NG signals in the tensor-tensor-tensor bispectrum, as well as mixed correlations such as tensor-tensor-scalar and tensor-scalar-scalar bispectra. Such NG signals would be testable by using the B-mode polarization, while the analysis of T -mode and E-mode bispectra provides quite limited information, even with the Planck resolution because of large contamination due to the scalar-scalar-scalar bispectrum (Meerburg et al 2016a;Domènech et al 2017;Bartolo et al 2019). In contrast, for models involving the axion and the gauge field, the tensor contribution dominates the scalar one at large scales and hence such a scalar-mode bias is negligible.…”

Section: Directional-dependent Ngmentioning

confidence: 99%

Planck2018 results

Akrami¹,

Arroja²,

Ashdown³

et al. 2020

A&A

409

118

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We analyse the Planck full-mission cosmic microwave background (CMB) temperature and E-mode polarization maps to obtain constraints on primordial non-Gaussianity (NG). We compare estimates obtained from separable template-fitting, binned, and optimal modal bispectrum estimators, finding consistent values for the local, equilateral, and orthogonal bispectrum amplitudes. Our combined temperature and polarization analysis produces the following final results: fNLlocal = −0.9 ± 5.1; fNLequil = −26 ± 47; and fNLortho = −38 ± 24 (68% CL, statistical). These results include low-multipole (4 ≤ ℓ < 40) polarization data that are not included in our previous analysis. The results also pass an extensive battery of tests (with additional tests regarding foreground residuals compared to 2015), and they are stable with respect to our 2015 measurements (with small fluctuations, at the level of a fraction of a standard deviation, which is consistent with changes in data processing). Polarization-only bispectra display a significant improvement in robustness; they can now be used independently to set primordial NG constraints with a sensitivity comparable to WMAP temperature-based results and they give excellent agreement. In addition to the analysis of the standard local, equilateral, and orthogonal bispectrum shapes, we consider a large number of additional cases, such as scale-dependent feature and resonance bispectra, isocurvature primordial NG, and parity-breaking models, where we also place tight constraints but do not detect any signal. The non-primordial lensing bispectrum is, however, detected with an improved significance compared to 2015, excluding the null hypothesis at 3.5σ. Beyond estimates of individual shape amplitudes, we also present model-independent reconstructions and analyses of the Planck CMB bispectrum. Our final constraint on the local primordial trispectrum shape is gNLlocal = (−5.8 ± 6.5) × 104 (68% CL, statistical), while constraints for other trispectrum shapes are also determined. Exploiting the tight limits on various bispectrum and trispectrum shapes, we constrain the parameter space of different early-Universe scenarios that generate primordial NG, including general single-field models of inflation, multi-field models (e.g. curvaton models), models of inflation with axion fields producing parity-violation bispectra in the tensor sector, and inflationary models involving vector-like fields with directionally-dependent bispectra. Our results provide a high-precision test for structure-formation scenarios, showing complete agreement with the basic picture of the ΛCDM cosmology regarding the statistics of the initial conditions, with cosmic structures arising from adiabatic, passive, Gaussian, and primordial seed perturbations.

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Section: Directional-dependent Ngmentioning

confidence: 99%

Planck2018 results

Akrami¹,

Arroja²,

Ashdown³

et al. 2020

A&A

409

118

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“…We derive an estimator for scalar 3-point functions that are sensitive to the presence of higher-spin fields during inflation [65,92,93] and provide estimators for 3-point functions that involve two or three tensor components. The 3-point functions with multiple tensor components are relevant for inflation models with pseudoscalar-gauge field interactions [37,[94][95][96], models with higher-derivative terms in the inflationary gravitational sector [97], and bimetric gravity models [98].…”

Section: Ae2mentioning

confidence: 99%

CMB B -mode non-Gaussianity: Optimal bispectrum estimator and Fisher forecasts

2020

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Upcoming cosmic microwave background (CMB) data can be used to explore harmonic 3-point functions that involve the B-mode component of the CMB polarization signal. We focus on bispectra describing the non-Gaussian correlation of the B-mode field and the CMB temperature anisotropies (T) and/or E-mode polarization, i.e., hTTBi, hEEBi, and hTEBi. Such bispectra probe violations of the tensor consistency relation: the model-independent behavior of cosmological correlation functions that involve a large-wavelength tensor mode (gravitational wave). An observed violation of the tensor consistency relation would exclude a large number of inflation models. We describe a generalization of the Komatsu-Spergel-Wandelt (KSW) bispectrum estimator that allows statistical inference on this type of primordial non-Gaussianity with data of the CMB temperature and polarization anisotropies. The generalized estimator shares its statistical properties with the existing KSW estimator and retains the favorable numerical scaling with angular resolution. In this paper, we derive the estimator and present a set of Fisher forecasts. We show how the forecasts scale with various experimental parameters such as minimum and maximum multipole moments, relevant for, e.g., the upcoming ground-based Simons Observatory experiment and proposed LiteBIRD satellite experiment. We comment on possible contaminants due to secondary cosmological and astrophysical sources.

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“…Existing studies of P-violating bispectra and trispectra [62][63][64][65][66][67][68][69][70][71][72][73][74][75] require the presence of either tensor modes or broken rotational symmetry. These studies are thus aimed to probe the P or CP of the inflaton background or the gravitational interactions.…”

Section: Introductionmentioning

confidence: 99%

Probing P and CP violations on the cosmological collider

Liu

Tong

Wang

et al. 2020

J. High Energ. Phys.

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In direct analogy to the 4-body decay of a heavy scalar particle, the 4-point correlation function of primordial fluctuations carries P and CP information. The CP violation appears as a P-odd angular dependence in the imaginary part of the trispectrum in momentum space. We construct a model with axion-like couplings which leads to observably large CP-violating trispectrum for future surveys. Furthermore, we show the importance of on-shell particle production in observing P-and CP-violating signals. It is impossible to observe these signals from local 4-scalar EFT operators that respect dS isometries, and thus any such observation can rule out single-field EFT with sufficiently small slow-roll parameters. This calculation opens a new frontier of studying P and CP at very high energy scales. * Electronic address: taoliu@ust.hk † Electronic address: xtongac@connect.ust.hk ‡ Electronic address: phyw@ust.hk § Electronic address:

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Measuring chiral gravitational waves in Chern-Simons gravity with CMB bispectra

Cited by 73 publications

References 47 publications

Planck2018 results

Planck2018 results

CMB B -mode non-Gaussianity: Optimal bispectrum estimator and Fisher forecasts

Probing P and CP violations on the cosmological collider

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