Bispectra from two-field inflation using the long-wavelength formalism

Tzavara, Eleftheria; Tent, B. Van

doi:10.1088/1475-7516/2011/06/026

Cited by 22 publications

(74 citation statements)

References 106 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is a broad literature on examples and specific realizations of this transfer mechanism from isocurvature to adiabatic perturbations (Bartolo et al 2002;Bernardeau & Uzan 2002;Vernizzi & Wands 2006;Rigopoulos et al 2006Rigopoulos et al , 2007Lyth & Rodriguez 2005;Tzavara & van Tent 2011; for a review on NG from multiple-field inflation models, see Byrnes & Choi 2010). An alternative, important possibility is the curvaton model (Mollerach 1990;Linde & Mukhanov 1997;Enqvist & Sloth 2002;Lyth & Wands 2002;Moroi & Takahashi 2001).…”

Section: Multi-field Modelsmentioning

confidence: 99%

Planck2015 results

Ade

Aghanim

Arnaud

et al. 2016

A&A

477

256

View full text Add to dashboard Cite

The Planck full mission cosmic microwave background (CMB) temperature and E-mode polarization maps are analysed to obtain constraints on primordial non-Gaussianity (NG). Using three classes of optimal bispectrum estimators -separable template-fitting (KSW), binned, and modalwe obtain consistent values for the primordial local, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result from temperature alone f local NL = 2.5 ± 5.7, f equil NL = −16 ± 70, and f ortho NL = −34 ± 33 (68% CL, statistical). Combining temperature and polarization data we obtain f local NL = 0.8 ± 5.0, f equil NL = −4 ± 43, and f ortho NL = −26 ± 21 (68% CL, statistical). The results are based on comprehensive cross-validation of these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are consistent with estimators based on measuring the Minkowski functionals of the CMB. The effect of time-domain de-glitching systematics on the bispectrum is negligible. In spite of these test outcomes we conservatively label the results including polarization data as preliminary, owing to a known mismatch of the noise model in simulations and the data. Beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and derive constraints on early universe scenarios that generate primordial NG, including general single-field models of inflation, axion inflation, initial state modifications, models producing parityviolating tensor bispectra, and directionally dependent vector models. We present a wide survey of scale-dependent feature and resonance models, accounting for the "look elsewhere" effect in estimating the statistical significance of features. We also look for isocurvature NG, and find no signal, but we obtain constraints that improve significantly with the inclusion of polarization. The primordial trispectrum amplitude in the local model is constrained to be g local NL = (−9.0 ± 7.7) × 10 4 (68% CL statistical), and we perform an analysis of trispectrum shapes beyond the local case. The global picture that emerges is one of consistency with the premises of the ΛCDM cosmology, namely that the structure we observe today was sourced by adiabatic, passive, Gaussian, and primordial seed perturbations.

show abstract

Section: Multi-field Modelsmentioning

confidence: 99%

Planck2015 results

Ade

Aghanim

Arnaud

et al. 2016

A&A

477

256

View full text Add to dashboard Cite

show abstract

“…This encompasses, for instance, a large class of multi-field models which leads to non-Gaussian isocurvature perturbations (for earlier works, see e.g., Linde & Mukhanov 1997;Peebles 1997;Bucher & Zhu 1997). More importantly, such models can also lead to cross-correlated and nonGaussian adiabatic and isocurvature modes, where NG is first generated by large nonlinearities in some scalar (possibly noninflatonic) sector of the theory, and then efficiently transferred to the inflaton adiabatic sector(s) through the cross-correlation of adiabatic and isocurvature perturbations 7 (Bartolo et al 2002;Bernardeau & Uzan 2002;Vernizzi & Wands 2006;Rigopoulos et al 2006Rigopoulos et al , 2007Lyth & Rodriguez 2005;Tzavara & van Tent 2011; for a review on NG from multiple-field inflation models, see, Byrnes & Choi 2010). Another interesting possibility is the curvaton model (Mollerach 1990;Enqvist & Sloth 2002;Lyth & Wands 2002;Moroi & Takahashi 2001), where a second light scalar field, subdominant during inflation, decays after inflation ends, producing the primordial density perturbations which can be characterized by a high NG level (e.g., Lyth & Wands 2002;Lyth et al 2003;Bartolo et al 2004d).…”

Section: Multi-field Modelsmentioning

confidence: 99%

Planck2013 results. XXIV. Constraints on primordial non-Gaussianity

Ade

Aghanim

Armitage-Caplan

et al. 2014

A&A

388

293

View full text Add to dashboard Cite

The Planck nominal mission cosmic microwave background (CMB) maps yield unprecedented constraints on primordial non-Gaussianity (NG). Using three optimal bispectrum estimators, separable template-fitting (KSW), binned, and modal, we obtain consistent values for the primordial local, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result f local NL = 2.7 ± 5.8, f equil NL = −42 ± 75, and f ortho NL = −25 ± 39 (68% CL statistical). Non-Gaussianity is detected in the data; using skew-C statistics we find a nonzero bispectrum from residual point sources, and the integrated-Sachs-Wolfe-lensing bispectrum at a level expected in the ΛCDM scenario. The results are based on comprehensive crossvalidation of these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are confirmed by skew-C , wavelet bispectrum and Minkowski functional estimators. Beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and thus derive constraints on early-Universe scenarios that generate primordial NG, including general single-field models of inflation, excited initial states (non-Bunch-Davies vacua), and directionally-dependent vector models. We provide an initial survey of scale-dependent feature and resonance models. These results bound both general single-field and multi-field model parameter ranges, such as the speed of sound, c s ≥ 0.02 (95% CL), in an effective field theory parametrization, and the curvaton decay fraction r D ≥ 0.15 (95% CL). The Planck data significantly limit the viable parameter space of the ekpyrotic/cyclic scenarios. The amplitude of the four-point function in the local model τ NL < 2800 (95% CL). Taken together, these constraints represent the highest precision tests to date of physical mechanisms for the origin of cosmic structure.

show abstract

“…So the first basis vector is always along the field trajectory as it is defined as the direction of the field velocity. The second basis vector is perpendicular to the first, and since we have only two dimensions it can be completely expressed in terms of the components of the first basis vector (see appendix A of [36] for some refinements of this basis originally introduced in [60]). For later use we will define the following quantities:…”

Section: Background Dynamicsmentioning

confidence: 99%

“…The aims of this paper are threefold. The first is a continuation of the work on the longwavelength formalism, in particular of [36]. In that paper a completely general expression for the f NL produced in two-field inflation on super-Hubble scales was derived.…”

mentioning

confidence: 99%

Non-Gaussianity in two-field inflation beyond the slow-roll approximation

Jung

Tent

2017

J. Cosmol. Astropart. Phys.

Self Cite

View full text Add to dashboard Cite

We use the long-wavelength formalism to investigate the level of bispectral non-Gaussianity produced in two-field inflation models with standard kinetic terms. Even though the Planck satellite has so far not detected any primordial non-Gaussianity, it has tightened the constraints significantly, and it is important to better understand what regions of inflation model space have been ruled out, as well as prepare for the next generation of experiments that might reach the important milestone of ∆f local NL = 1. We derive an alternative formulation of the previously derived integral expression for f NL , which makes it easier to physically interpret the result and see which types of potentials can produce large non-Gaussianity. We apply this to the case of a sum potential and show that it is very difficult to satisfy simultaneously the conditions for a large f NL and the observational constraints on the spectral index n s . In the case of the sum of two monomial potentials and a constant we explicitly show in which small region of parameter space this is possible, and we show how to construct such a model. Finally, the new general expression for f NL also allows us to prove that for the sum potential the explicit expressions derived within the slow-roll approximation remain valid even when the slow-roll approximation is broken during the turn of the field trajectory (as long as only the slow-roll parameter remains small). arXiv:1611.09233v2 [astro-ph.CO] 11 May 20173 At first order and in the flat gauge we are using here (where the scale factor a is homogeneous), ζm = − κ √ 2 emAδφ A . For the generalized definition at higher order and various gauge issues, see the cited literature.

show abstract

Bispectra from two-field inflation using the long-wavelength formalism

Cited by 22 publications

References 106 publications

Planck2015 results

Planck2015 results

Planck2013 results. XXIV. Constraints on primordial non-Gaussianity

Non-Gaussianity in two-field inflation beyond the slow-roll approximation

Contact Info

Product

Resources

About