scholarly journals Swampland Conjecture and Inflation Model from Brane Perspective

2021 ◽  
Author(s):  
Jafar Sadeghi ◽  
B Pourhassan ◽  
Saeed Noorigashti ◽  
Sudhaker Upadhyay
Keyword(s):  
Spectral Index ◽  
Cosmological Parameters ◽  
Expanding Universe ◽  
The Past ◽  
Inflation Model ◽  
Gravitational Model ◽  
Observable Data

Abstract Over the past few decades, inflation models have been studied by researchers from different perspectives and conditions in order to introduce a model for the expanding universe. In this paper, we introduce a modified f(R) gravitational model as (R + γRp ) in order to examine a new condition for inflation models. Given that our studies are related to a modified f(R) gravitational model on the brane, therefore we will encounter modified cosmological parameters. So, we first introduce these modified cosmological parameters such as spectral index, a number of e-folds and etc. Then, we apply these conditions to our modified f(R) gravitational model in order to adapt to the swampland criteria. Finally, we determine the range of each of these parameters by plotting some figures and with respect to observable data such as Planck 2018.

scholarly journals NONCOMMUTATIVE DECRUMPLING INFLATION AND RUNNING OF THE SPECTRAL INDEX

2005 ◽  
Vol 14 (03n04) ◽  
pp. 621-633 ◽  
Author(s):  
FOROUGH NASSERI ◽  
S. A. ALAVI
Keyword(s):  
Noncommutative Geometry ◽  
Spectral Index ◽  
Time Variability ◽  
Inflation Model ◽  
Slow Roll ◽  
Spatial Dimensions

We present a new inflation model, known as noncommutative decrumpling inflation, in which space has noncommutative geometry with time variability of the number of spatial dimensions. Within the framework of noncommutative decrumpling inflation, we compute both the spectral index and its running. Our results show the effects of both time variability of the number of spatial dimensions and noncommutative geometry on the spectral index and its running. Two classes of examples have been studied and comparisons made with the standard slow-roll formulae. We conclude that the effects of noncommutative geometry on the spectral index and its running are much smaller than the effects of time variability of spatial dimensions.

scholarly journals BICEP2 constrains composite inflation

2014 ◽  
Vol 23 (08) ◽  
pp. 1450070 ◽  
Author(s):  
Phongpichit Channuie
Keyword(s):  
Spectral Index ◽  
Cosmological Parameters ◽  
Inflationary Model ◽  
Composite State ◽  
Planck Data ◽  
Strongly Coupled ◽  
Yang Mills ◽  
Composite Models ◽  
Single Field ◽  
Inflationary Models

In light of BICEP2, we re-examine single field inflationary models in which the inflation is a composite state stemming from various four-dimensional strongly coupled theories. We study in the Einstein frame a set of cosmological parameters, the primordial spectral index ns and tensor-to-scalar ratio r, predicted by such models. We confront the predicted results with the joint Planck data, and with the recent BICEP2 data. We constrain the number of e-foldings for composite models of inflation in order to obtain a successful inflation. We find that the minimal composite inflationary model is fully consistent with the Planck data. However it is in tension with the recent BICEP2 data. The observables predicted by the glueball inflationary model can be consistent with both Planck and BICEP2 contours if a suitable number of e-foldings are chosen. Surprisingly, the super Yang–Mills inflationary prediction is significantly consistent with the Planck and BICEP2 observations.

scholarly journals Reconstructing the Primordial Power Spectrum

2005 ◽  
Vol 216 ◽  
pp. 28-34
Author(s):  
S. L. Bridle ◽  
A. M. Lewis ◽  
J. Weller ◽  
G. Efstathiou
Keyword(s):  
Power Spectrum ◽  
Spectral Index ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Microwave Background ◽  
Primordial Power Spectrum ◽  
Initial Spectrum ◽  
Redshift Survey ◽  
Cosmic Microwave Background Data

We reconstruct the shape of the primordial power spectrum from the latest cosmic microwave background data, including the new results from the Wilkinson Microwave Anisotropy Probe (WMAP), and large scale structure data from the two degree field galaxy redshift survey (2dFGRS). We discuss two parameterizations taking into account the uncertainties in four cosmological parameters. First we parameterize the initial spectrum by a tilt and a running spectral index, finding marginal evidence for a running spectral index only if the first three WMAP multipoles (ℓ = 2, 3, 4) are included in the analysis. Secondly, to investigate further the low CMB large scale power, we modify the conventional power-law spectrum by introducing a scale above which there is no power. We find a preferred position of the cut at kc ∼ 3 × 10--4 Mpc--1 although kc = 0 (no cut) is not ruled out.

scholarly journals Constraint on inflation model from BICEP2 and WMAP 9-year data

2015 ◽  
Vol 24 (04) ◽  
pp. 1541001 ◽  
Author(s):  
Cheng Cheng ◽  
Qing-Guo Huang
Keyword(s):  
Power Law ◽  
Hubble Space Telescope ◽  
Wave Spectrum ◽  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Tensor Model ◽  
Scale Invariant ◽  
Inflation Model ◽  
Inverse Power Law

Even though Planck data released in 2013 (P13) is not compatible with Background Imaging of Cosmic Extragalactic Polarization (B2) and some local cosmological observations, including Supernova Legacy Survey (SNLS) samples and H0 prior from Hubble Space Telescope (HST) etc. Wilkinson Microwave Anisotropy Probe 9-year data (W9) is consistent with all of them in the base six-parameter ΛCDM + tensor cosmology quite well. In this paper, we adopt the combinations of B2+W9 and B2+W9+SNLS+BAO+HST to constrain the cosmological parameters in the base six-parameter ΛCDM + tensor model with nt = -r/8, where r and nt are the tensor-to-scalar ratio and the tilt of relic gravitational wave spectrum, and BAO denotes Baryon Acoustic Oscillation (BAO). We find that the Harrison–Zel'dovich (HZ) scale invariant scalar power spectrum is consistent with both data combinations, chaotic inflation is marginally disfavored by the data at around 2σ level, but the power-law inflation model and the inflation model with inverse power-law potential can fit the data nicely.

scholarly journals HIGGS INFLATION IN f(Φ, R) THEORY

2014 ◽  
Vol 23 (04) ◽  
pp. 1450029 ◽  
Author(s):  
GIRISH KUMAR CHAKRAVARTY ◽  
SUBHENDRA MOHANTY ◽  
NAVEEN K. SINGH
Keyword(s):  
Scalar Curvature ◽  
Spectral Index ◽  
Early Universe ◽  
Coupling Parameter ◽  
Planck Scale ◽  
Higgs Field ◽  
Coupling Model ◽  
Order Unity ◽  
Inflation Model ◽  
Higher Dimensional

We generalize the scalar-curvature coupling model ξΦ2R of Higgs inflation to ξΦaRb to study inflation. We compute the amplitude and spectral index of curvature perturbations generated during inflation and fix the parameters of the model by comparing these with the Planck + WP data. We find that if the scalar self-coupling λ is in the range 10-5–0.1, parameter a in the range 2.3–3.6 and b in the range 0.77–0.22 at the Planck scale, one can have a viable inflation model even for ξ ≃ 1. The tensor to scalar ratio r in this model is small and our model with scalar-curvature couplings is not ruled out by observational limits on r unlike the pure [Formula: see text] theory. By requiring the curvature coupling parameter to be of order unity, we have evaded the problem of unitarity violation in scalar-graviton scatterings which plague the ξΦ2R Higgs inflation models. We conclude that the Higgs field may still be a good candidate for being the inflaton in the early universe if one considers higher-dimensional curvature coupling.

scholarly journals Evolution of the Radio Emission from Young SNRs according to Observational Data

1979 ◽  
Vol 32 (2) ◽  
pp. 95 ◽  
Author(s):  
KS Stankevich
Keyword(s):  
Experimental Data ◽  
Radio Emission ◽  
Flux Density ◽  
Observational Data ◽  
Spectral Index ◽  
Density Measurements ◽  
The Past ◽  
Absolute Flux ◽  
Density Decrease ◽  
Frequency Variations

Results are given from a still-continuing series of absolute flux density measurements for the SNR CasA. The measurements have been taken regularly over the past 16 years at 24 wavelengths in the range 3-60 cm. New data are presented for the rate of flux density decrease, and for time and frequency variations in the spectral index. Intensity increases that are localized in frequency are described. The results are generalized in a model for the radio emission from a young SNR, and this is used to analyse experimental data for flux density decreases in the emission from 3C 10 and 58.

Study of some cosmological parameters in logarithmic corrected f(R) gravitational model with swampland conjectures

2020 ◽  
pp. 2150027
Author(s):  
J. Sadeghi ◽  
E. Naghd Mezerji ◽  
S. Noori Gashti
Keyword(s):  
Polynomial Function ◽  
Cosmological Parameters ◽  
Low Energy ◽  
Index Formula ◽  
Quantum Field ◽  
Logarithmic Term ◽  
Slow Roll ◽  
Gravitational Model ◽  
Energy Quantum ◽  
Lower Limits

In this paper, we use corrected [Formula: see text] gravitational model which is a polynomial function with a logarithmic term. We employ the slow-roll conditions and obtain the number of cosmological parameters. This helps us to verify the swampland conjectures which guarantees validation of low energy quantum field theory. The obtained results show that the corresponding model is consistent with the swampland conjectures. Also, the upper and lower limits of the parameter [Formula: see text] are, respectively, 0.15 and 0.0033. Finally, by using scalar spectrum index [Formula: see text] and tensor-to-scalar ratio [Formula: see text] relations and comparing with the Planck 2018 data, we obtain the coefficients [Formula: see text], [Formula: see text] and [Formula: see text]. Also, the corresponding results are constructed by several figures, literature and also Planck 2018 data.

PERTURBATIONS FROM D-TERM INFLATION

2007 ◽  
Vol 22 (25n28) ◽  
pp. 2035-2038
Author(s):  
OSAMU SETO ◽  
JUN'ICHI YOKOYAMA
Keyword(s):  
Spectral Index ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Unit Length ◽  
Higher Order ◽  
Inflation Model ◽  
Scalar Spectral Index ◽  
String Problem ◽  
Kähler Potential ◽  
Higher Order Corrections

We investigated a simple D-term inflation with taking account of higher order corrections in the Kähler potential. These terms may solve the cosmic string problem in D-term inflation model. The mass per unit length of cosmic strings formed after inflation can be suppressed enough. In addition, the change of the potential slope leads simultaneously a more tilted scalar spectral index ns ≃ 0.96 – 0.97 than that in the model without these corrections.

scholarly journals TRANS-PLANCKIAN PHYSICS AND NON-COMMUTATIVE INFLATION

2008 ◽  
Vol 23 (17n20) ◽  
pp. 1598-1605 ◽  
Author(s):  
SEOKTAE KOH
Keyword(s):  
Scalar Field ◽  
Thermal Radiation ◽  
Spectral Index ◽  
Planck Scale ◽  
Dispersion Relations ◽  
Scale Invariant ◽  
Inflation Model

Non-commutativity of spacetime at the Planck scale may deform the usual dispersion relations. And these deformed dispersion relations could lead to the accelerating phase without a scalar field. In this paper, we have calculated the spectral index and the running of spectral index in a non-commutative inflation model. Non-commutative inflation with thermal radiation gives a scale invariant spectrum in the limit w → −1 and negative running spectral index which are consistent with the WMAP 3-year results.

scholarly journals Take up the challenge for a single field inflation after BICEP2

2014 ◽  
Vol 29 (36) ◽  
pp. 1450197 ◽  
Author(s):  
Chao-Jun Feng ◽  
Xin-Zhou Li
Keyword(s):  
Power Series ◽  
Spectral Index ◽  
Big Bang ◽  
Absolute Value ◽  
Inflation Model ◽  
The Absolute ◽  
Powerful Constraint ◽  
Single Field ◽  
Ips Model

The measurement of the tensor-to-scalar ratio r shows a very powerful constraint to theoretical inflation models through the detection of B-mode. In this paper, we propose a single inflation model with infinity power series potential called the Infinity Power Series (IPS) inflation model, which is well consistent with latest observations from Planck and BICEP2. Furthermore, it is found that in the IPS model, the absolute value running of the spectral index increases while the tensor-to-scalar ratio becomes large, namely both large r ≈0.20 and [Formula: see text] are realized in the IPS model. In the meanwhile, the number of e-folds is also big enough N≈50–60 to solve the problems in Big Bang cosmology.

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