scholarly journals Quantum-Gravitational Effects on Primordial Power Spectra in Slow-Roll Inflationary Models

Galaxies ◽  
2018 ◽  
Vol 6 (1) ◽  
pp. 6 ◽  
Author(s):  
David Brizuela ◽  
Manuel Krämer
Keyword(s):  
Power Spectra ◽  
Gravitational Effects ◽  
Slow Roll ◽  
Inflationary Models

scholarly journals Planck 2018 results

2020 ◽  
Vol 641 ◽  
pp. A10 ◽  
Author(s):  
◽  
Y. Akrami ◽  
F. Arroja ◽  
M. Ashdown ◽  
J. Aumont ◽  
...  
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Acoustic Oscillation ◽  
Physical Models ◽  
Polarization Data ◽  
Slow Roll ◽  
Single Field ◽  
Inflationary Models

We report on the implications for cosmic inflation of the 2018 release of the Planck cosmic microwave background (CMB) anisotropy measurements. The results are fully consistent with those reported using the data from the two previous Planck cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles. Planck temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be ns = 0.9649 ± 0.0042 at 68% CL. We find no evidence for a scale dependence of ns, either as a running or as a running of the running. The Universe is found to be consistent with spatial flatness with a precision of 0.4% at 95% CL by combining Planck with a compilation of baryon acoustic oscillation data. The Planck 95% CL upper limit on the tensor-to-scalar ratio, r0.002 <  0.10, is further tightened by combining with the BICEP2/Keck Array BK15 data to obtain r0.002 <  0.056. In the framework of standard single-field inflationary models with Einstein gravity, these results imply that: (a) the predictions of slow-roll models with a concave potential, V″(ϕ) < 0, are increasingly favoured by the data; and (b) based on two different methods for reconstructing the inflaton potential, we find no evidence for dynamics beyond slow roll. Three different methods for the non-parametric reconstruction of the primordial power spectrum consistently confirm a pure power law in the range of comoving scales 0.005 Mpc−1 ≲ k ≲ 0.2 Mpc−1. A complementary analysis also finds no evidence for theoretically motivated parameterized features in the Planck power spectra. For the case of oscillatory features that are logarithmic or linear in k, this result is further strengthened by a new combined analysis including the Planck bispectrum data. The new Planck polarization data provide a stringent test of the adiabaticity of the initial conditions for the cosmological fluctuations. In correlated, mixed adiabatic and isocurvature models, the non-adiabatic contribution to the observed CMB temperature variance is constrained to 1.3%, 1.7%, and 1.7% at 95% CL for cold dark matter, neutrino density, and neutrino velocity, respectively. Planck power spectra plus lensing set constraints on the amplitude of compensated cold dark matter-baryon isocurvature perturbations that are consistent with current complementary measurements. The polarization data also provide improved constraints on inflationary models that predict a small statistically anisotropic quadupolar modulation of the primordial fluctuations. However, the polarization data do not support physical models for a scale-dependent dipolar modulation. All these findings support the key predictions of the standard single-field inflationary models, which will be further tested by future cosmological observations.

scholarly journals Gauge inflation by kinetic coupled gravity

2014 ◽  
Vol 29 (30) ◽  
pp. 1450161 ◽  
Author(s):  
F. Darabi ◽  
A. Parsiya
Keyword(s):  
Field Theory ◽  
Gauge Field ◽  
Gauge Field Theory ◽  
Einstein Tensor ◽  
Abelian Gauge ◽  
Metric Tensor ◽  
New Class ◽  
Slow Roll ◽  
Set Up ◽  
Inflationary Models

Recently, a new class of inflationary models, so-called gauge-flation or non-Abelian gauge field inflation has been introduced where the slow-roll inflation is driven by a non-Abelian gauge field A with the field strength F. This class of models are based on a gauge field theory having F2 and F4 terms with a non-Abelian gauge group minimally coupled to gravity. Here, we present a new class of such inflationary models based on a gauge field theory having only F2 term with non-Abelian gauge fields non-minimally coupled to gravity. The non-minimal coupling is set up by introducing the Einstein tensor besides the metric tensor within the F2 term, which is called kinetic coupled gravity. A perturbation analysis is performed to confront the inflation under consideration with Planck and BICEP2 results

On Primordial Black Holes and secondary gravitational waves generated from inflation with solo/multi-bumpy potential

2021 ◽  
Author(s):  
Rui feng Zheng ◽  
Jia ming Shi ◽  
Taotao Qiu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Waves ◽  
Power Spectra ◽  
Small Scale ◽  
Primordial Black Hole ◽  
Primordial Black Holes ◽  
Slow Roll ◽  
Spherical Collapse ◽  
Scalar Perturbations

Abstract It is well known that primordial black hole (PBH) can be generated in inflation process of the early universe, especially when the inflaton field has some non-trivial features that could break the slow-roll condition. In this paper, we investigate a toy model of inflation with bumpy potential, which has one or several bumps. We found that potential with multi-bump can give rise to power spectra with multi peaks in small-scale region, which can in turn predict the generation of primordial black holes in various mass ranges. We also consider the two possibilities of PBH formation by spherical collapse and elliptical collapse. And discusses the scalar-induced gravitational waves (SIGWs) generated by the second-order scalar perturbations.

scholarly journals Inflationary perturbation spectra at next-to-leading slow-roll order in effective field theory of inflation

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Guang-Hua Ding ◽  
Jin Qiao ◽  
Qiang Wu ◽  
Tao Zhu ◽  
Anzhong Wang
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
High Energy Physics ◽  
Power Spectra ◽  
High Energy ◽  
Effective Field ◽  
Spectral Indices ◽  
Leading Order ◽  
Slow Roll ◽  
Tensor Perturbations

AbstractThe effective field theory (EFT) of inflation provides an essential picture to explore the effects of the unknown high energy physics in the single scalar field inflation models. For a generic EFT of inflation, possible high energy corrections to simple slow-roll inflation can modify both the propagating speed and dispersion relations of the cosmological scalar and tensor perturbations. With the arrival of the era of precision cosmology, it is expected that these high energy corrections become more important and have to be taken into account in the analysis with future precise observational data. In this paper we study the observational predictions of the EFT of inflation by using the third-order uniform asymptotic approximation method. We calculate explicitly the primordial power spectra, spectral indices, running of the spectral indices for both scalar and tensor perturbations, and the ratio between tensor and scalar spectra. These expressions are all written in terms of the Hubble flow parameters and the flow of four new slow-roll parameters and expanded up to the next-to-leading order in the slow-roll expansions so they represent the most accurate results obtained so far in the literature. The flow of the four new slow-roll parameters, which arise from the four new operators introduced in the action of the EFT of inflation, can affect the primordial perturbation spectra at the leading-order and the corresponding spectral indices at the next-to-leading order.

scholarly journals Constraints on features in the inflationary potential from future Euclid data

2020 ◽  
Vol 496 (3) ◽  
pp. 3448-3468
Author(s):  
Ivan Debono ◽  
Dhiraj Kumar Hazra ◽  
Arman Shafieloo ◽  
George F Smoot ◽  
Alexei A Starobinsky
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
Large Scale ◽  
Strong Support ◽  
Power Spectra ◽  
Spectral Amplitude ◽  
Microwave Background ◽  
Slow Roll ◽  
Primordial Power Spectrum ◽  
Small Scales

ABSTRACT With Planck cosmic microwave background observations, we established the spectral amplitude and tilt of the primordial power spectrum. Evidence of a red spectral tilt (ns = 0.96) at 8σ provides strong support for the inflationary mechanism, especially the slow roll of the effective scalar field in its nearly flat potential as the generator of scalar primordial perturbations. With the next generation of large-scale structure surveys, we expect to probe primordial physics beyond the overall shape and amplitude of the main, smooth, and slowly changing part of the inflaton potential. Using the specifications for the upcoming Euclid survey, we investigate to what extent we can constrain the inflation potential beyond its established slow-roll behaviour. We provide robust forecasts with Euclid and Planck mock data from nine fiducial power spectra that contain suppression and wiggles at different cosmological scales, using the Wiggly Whipped Inflation (WWI) framework to generate these features in the primordial spectrum. We include both Euclid cosmic shear and galaxy clustering, with a conservative cut-off for non-linear scales. Using Markov chain Monte Carlo simulations, we obtain an improvement in constraints in the WWI potential, as well an improvement for the background cosmology parameters. We find that apart from improving the constraints on the overall scale of the inflationary potential by 40–50 per cent, we can also identify oscillations in the primordial spectrum that are present within intermediate to small scales ($k\sim 0.01\!-\!0.2\, \mathrm{Mpc^{-1}}$).

Shaft potential inspired warm inflation

2017 ◽  
Vol 14 (06) ◽  
pp. 1750088 ◽  
Author(s):  
Abdul Jawad ◽  
Amara Ilyas ◽  
Sarfraz Ahmad
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Power Spectra ◽  
Spectral Indices ◽  
Tensor Power ◽  
Planck Data ◽  
Warm Inflation ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Inflationary Parameters

We discuss the warm inflation in the presence of shaft potential [Formula: see text], tachyon scalar field and the generalized form of dissipative coefficient [Formula: see text]. In this respect, we investigate the inflationary parameters (slow-roll parameters, number of e-folds, scalar-tensor power spectra, spectral indices, tensor-to-scalar ratio and running of scalar spectral index) in both strong and weak dissipative regimes. It is interesting to mention that our inflationary parametric results (tensor-scalar ratio, spectral index and running of spectral) are consistent with the recent observational data such as BICEP[Formula: see text], WMAP[Formula: see text] and latest Planck data.

scholarly journals A BACK-REACTION INDUCED LOWER BOUND ON THE TENSOR-TO-SCALAR RATIO

2008 ◽  
Vol 23 (10) ◽  
pp. 727-735 ◽  
Author(s):  
PATRICK MARTINEAU ◽  
ROBERT BRANDENBERGER
Keyword(s):  
Lower Bound ◽  
Gravitational Waves ◽  
Power Spectra ◽  
Back Reaction ◽  
Scale Invariant ◽  
Large Classes ◽  
Higher Order Terms ◽  
Scalar Amplitude ◽  
Inflationary Models ◽  
Metric Fluctuations

There are large classes of inflationary models, particularly popular in the context of string theory and braneworld approaches to inflation, in which the ratio of linearized tensor-to-scalar metric fluctuations is very small. In such models, however, gravitational waves produced by scalar modes cannot be neglected. We derive the lower bound on the tensor-to-scalar ratio by considering the back-reaction of the scalar perturbations as a source of gravitational waves. These results show that no cosmological model that is compatible with a metric scalar amplitude of ≈10-5 can have a ratio of the tensor-to-scalar power spectra less than ≈10-8 at recombination and that higher-order terms leads to logarithmic growth for r during radiation domination. Our lower bound also applies to non-inflationary models which produce an almost scale-invariant spectrum of coherent super-Hubble scale metric fluctuations.

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