Running of the scalar spectral index in bouncing cosmologies

In this paper we investigate the observational signatures of Loop Quantum Cosmology (LQC) in the CMB data. First, we concentrate on the dynamics of LQC and we provide the basic cosmological functions. We then obtain the power spectrum of scalar and tensor perturbations in order to study the performance of LQC against the latest CMB data. We find that LQC provides a robust prediction for the main slow-roll parameters, like the scalar spectral index and the tensor-to-scalar fluctuation ratio, which are in excellent agreement within [Formula: see text] with the values recently measured by the Planck collaboration. This result indicates that LQC can be seen as an alternative scenario with respect to that of standard inflation.

Download Full-text

Large tensor-to-scalar ratio and running of the scalar spectral index with instep inflation

Physical Review D ◽

10.1103/physrevd.91.043502 ◽

2015 ◽

Vol 91 (4) ◽

Cited By ~ 10

Author(s):

Guillermo Ballesteros ◽

J. Alberto Casas

Keyword(s):

Spectral Index ◽

Scalar Spectral Index

Download Full-text

α-Attractors and reheating in a nonminimal inflationary model

International Journal of Modern Physics D ◽

10.1142/s0218271820500777 ◽

2020 ◽

Vol 29 (10) ◽

pp. 2050077

Author(s):

R. Shojaee ◽

K. Nozari ◽

F. Darabi

Keyword(s):

Scalar Field ◽

Spectral Index ◽

Parameter Space ◽

Model Potential ◽

Index Formula ◽

Inflationary Model ◽

Scalar Spectral Index ◽

Canonical Scalar Field

We study [Formula: see text]-attractor models with both E-model and T-model potential in an extended Nonminimal Derivative (NMD) inflation where a canonical scalar field and its derivatives are nonminimally coupled to gravity. We calculate the evolution of perturbations during this regime. Then by adopting inflation potentials of the model we show that in the large [Formula: see text] and small [Formula: see text] limit, the value of the scalar spectral index [Formula: see text] and tensor-to-scalar ratio [Formula: see text] are universal. Next, we study reheating after inflation in this formalism. We obtain some constraints on the model’s parameter space by adopting the results with Planck 2018.

Download Full-text

Unlocking the synergy between CMB spectral distortions and anisotropies

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2021/12/050 ◽

2021 ◽

Vol 2021 (12) ◽

pp. 050

Author(s):

Hao Fu ◽

Matteo Lucca ◽

Silvia Galli ◽

Elia S. Battistelli ◽

Deanna C. Hooper ◽

...

Keyword(s):

Spectral Index ◽

Big Bang ◽

Noise Levels ◽

Microwave Background ◽

Big Bang Nucleosynthesis ◽

Scalar Spectral Index ◽

New Information ◽

Wide Range ◽

Inflationary Parameters ◽

Better Than

Abstract Measurements of the cosmic microwave background (CMB) spectral distortions (SDs) will open a new window on the very early universe, providing new information complementary to that gathered from CMB temperature and polarization anisotropies. In this paper, we study their synergy as a function of the characteristics of the considered experiments. In particular, we examine a wide range of sensitivities for possible SD measurements, spanning from FIRAS up to noise levels 1000 times better than PIXIE, and study their constraining power when combined with current or future CMB anisotropy experiments such as Planck or LiteBIRD plus CMB-S4. We consider a number of different cosmological models such as the ΛCDM, as well as its extensions with the running of the scalar spectral index, the decay or the annihilation of dark matter (DM) particles. While upcoming CMB anisotropy experiments will be able to decrease the uncertainties on inflationary parameters such as As and ns by about a factor 2 in the ΛCDM case, we find that an SD experiment 100 times more sensitive than PIXIE (comparable to the proposed Super-PIXIE satellite) could potentially further contribute to constrain these parameters. This is even more significant in the case of the running of the scalar spectral index. Furthermore, as expected, constraints on DM particles decaying at redshifts probed by SDs will improve by orders of magnitude even with an experiment 10 times worse than PIXIE as compared to CMB anisotropies or Big Bang Nucleosynthesis bounds. On the contrary, DM annihilation constraints will not significantly improve over CMB anisotropy measurements. Finally, we forecast the constraints obtainable with sensitivities achievable either from the ground or from a balloon.

Download Full-text

Dynamics of tachyon fields and inflation - comparison of analytical and numerical results with observation

Serbian Astronomical Journal ◽

10.2298/saj160312003m ◽

2016 ◽

pp. 1-8 ◽

Cited By ~ 4

Author(s):

M. Milosevic ◽

D.D. Dimitrijevic ◽

G.S. Djordjevic ◽

M.D. Stojanovic

Keyword(s):

Scalar Field ◽

String Theory ◽

Numerical Methods ◽

Spectral Index ◽

Early Universe ◽

Slow Roll ◽

Scalar Spectral Index ◽

Homogeneous Universe ◽

The Given ◽

Good Agreement

The role tachyon fields may play in evolution of early universe is discussed in this paper. We consider the evolution of a flat and homogeneous universe governed by a tachyon scalar field with the DBI-type action and calculate the slow-roll parameters of inflation, scalar spectral index (n), and tensor-scalar ratio (r) for the given potentials. We pay special attention to the inverse power potential, first of all to V (x) ~ x?4, and compare the available results obtained by analytical and numerical methods with those obtained by observation. It is shown that the computed values of the observational parameters and the observed ones are in a good agreement for the high values of the constant X0. The possibility that influence of the radion field can extend a range of the acceptable values of the constant X0 to the string theory motivated sector of its values is briefly considered.

Download Full-text

Reconstruction of warm Chaplygin gas inflationary models

Modern Physics Letters A ◽

10.1142/s0217732320502685 ◽

2020 ◽

Vol 35 (32) ◽

pp. 2050268

Author(s):

Abdul Jawad ◽

Shamaila Rani ◽

Kazuharu Bamba ◽

Nadeem Azhar

Keyword(s):

Spectral Index ◽

Effective Potential ◽

Chaplygin Gas ◽

Index Formula ◽

Curvature Perturbation ◽

Warm Inflation ◽

Scalar Spectral Index ◽

Dissipative Coefficient ◽

Inflationary Parameters ◽

Friedmann Robertson Walker

By assuming the specific Chaplygin gas model, we study the reconstruction of warm inflation model with the help of tensor-to-scalar ratio [Formula: see text] and scalar spectral index [Formula: see text]. In this regard, we take flat Friedmann–Robertson–Walker (FRW) metric and discuss the general forms of dissipative coefficient [Formula: see text] as well as effective potential [Formula: see text] for two dissipative regimes i.e., the weak and strong. We use inflationary parameters such as slow-roll parameters, power spectrum of the curvature perturbation, tensor spectrum, spectral index, scalar-to-tensor ratio and Hubble parameter to find the generalized form of dissipative coefficient and effective potential. We discuss the results of dissipative coefficient and reconstructed potential in detail for the specific choice of tensor-to-scalar ratio [Formula: see text] and scalar spectral index [Formula: see text].

Download Full-text

WHAT IF THE INFLATON IS A SPINOR CONDENSATE?

International Journal of Modern Physics D ◽

10.1142/s0218271809016181 ◽

2009 ◽

Vol 18 (14) ◽

pp. 2173-2179 ◽

Cited By ~ 26

Author(s):

S. SHANKARANARAYANAN

Keyword(s):

Scalar Field ◽

Gravitational Wave ◽

Spectral Index ◽

Spinor Condensate ◽

Slow Roll ◽

Scalar Spectral Index ◽

The Future ◽

Wmap Data ◽

Elementary Field ◽

Canonical Scalar Field

In the usual cosmological inflationary scenarios, the scalar field — the inflaton — is usually assumed to be an elementary field. In this essay, we ask: What are the observational signatures if the scalar field is a spinor condensate? And is there a way to distinguish between the canonical scalar field and the spinor-condensate-driven models? In the homogeneous and isotropic background, we show that — although the dark-spinor (Elko) condensate leads to an acceleration equation identical to that of the canonical-scalar-field-driven inflation — the dynamics of the two models are different. In the slow-roll limit, we show that the model predicts a running of the scalar spectral index consistent with the WMAP data. We show that the consistency relations between the spinor condensate and the canonical-scalar-field-driven model are different, which we will be able to test using the future CMB and gravitational wave missions.

Download Full-text

PERTURBATIONS FROM D-TERM INFLATION

Modern Physics Letters A ◽

10.1142/s0217732307025273 ◽

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.

Download Full-text

New constraint of an attractor GL model in braneworld context

International Journal of Modern Physics A ◽

10.1142/s0217751x17501196 ◽

2017 ◽

Vol 32 (19n20) ◽

pp. 1750119

Author(s):

Z. Mounzi ◽

A. Safsafi ◽

M. Ferricha-Alami ◽

M. Bennai

Keyword(s):

Power Spectrum ◽

Spectral Index ◽

Index Formula ◽

Brane Tension ◽

Inflation Model ◽

Scalar Spectral Index ◽

Central Value ◽

Braneworld Model ◽

Inflationary Parameters

We are interested in studying the generalization of the first chaotic inflation model in supergravity, which was proposed by Goncharov and Linde (GL model) and was recently revisited, in the framework of the Randall–Sundrum type 2 braneworld model. This model predicts a tiny ratio [Formula: see text] and [Formula: see text]. Our scenario predicts a great tensor-to-scalar ratio [Formula: see text] of the order [Formula: see text] and the central value of the scalar spectral index [Formula: see text] for a particular choice of values of brane tension [Formula: see text] and the parameter [Formula: see text]. We have shown that this scenario reproduces successfully an attractor behavior. We have also derived all known spectrum inflationary parameters, in particular the running [Formula: see text] and the power spectrum of the curvature perturbations [Formula: see text] which are widely consistent with Planck observations.

Download Full-text

Shaft potential inspired warm inflation

International Journal of Geometric Methods in Modern Physics ◽

10.1142/s0219887817500888 ◽

2017 ◽

Vol 14 (06) ◽

pp. 1750088 ◽

Cited By ~ 1

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.

Download Full-text