scholarly journals Einstein-singleton theory and its power spectra in de Sitter inflation

2016 ◽  
Vol 25 (14) ◽  
pp. 1650107
Author(s):  
Yun Soo Myung ◽  
Taeyoon Moon ◽  
Young-Jai Park
Keyword(s):  
Fourth Order ◽  
Power Spectra ◽  
Integral Function ◽  
De Sitter ◽  
Scale Invariant ◽  
Exponential Integral ◽  
Scalar Theory ◽  
Inflation Model ◽  
Slow Roll ◽  
Sitter Spacetime

We study the Einstein-singleton theory during de Sitter inflation since it provides a way to degenerate fourth-order scalar theory. We obtain an exact solution expressed in terms of the exponential-integral function by solving the degenerate fourth-order scalar equation in de Sitter spacetime. Furthermore, we find that its power spectrum blows negatively up in the superhorizon limit, while it is negatively scale-invariant in the subhorizon limit. This suggests that the Einstein-singleton theory contains the ghost-instability and thus, it is not suitable for developing a slow-roll inflation model.

scholarly journals Scale-invariant scalar spectrum from the nonminimal derivative coupling with fourth-order term

2015 ◽  
Vol 24 (14) ◽  
pp. 1550095 ◽  
Author(s):  
Yun Soo Myung ◽  
Taeyoon Moon
Keyword(s):  
Fourth Order ◽  
Order Term ◽  
Order Derivative ◽  
Scalar Perturbation ◽  
De Sitter ◽  
Scale Invariant ◽  
Derivative Coupling ◽  
Sitter Spacetime ◽  
Fourth Order Term ◽  
Derivative Term

In this paper, an exactly scale-invariant spectrum of scalar perturbation generated during de Sitter spacetime is found from the gravity model of the nonminimal derivative coupling with fourth-order term. The nonminimal derivative coupling term generates a healthy (ghost-free) fourth-order derivative term, while the fourth-order term provides an unhealthy (ghost) fourth-order derivative term. The Harrison–Zel’dovich spectrum obtained from Fourier transforming the fourth-order propagator in de Sitter space is recovered by computing the power spectrum in its momentum space directly. It shows that this model provides a truly scale-invariant spectrum, in addition to the Lee–Wick scalar theory.

INFLATION IN KALUZA-KLEIN COSMOLOGY II: FRIEDMANN MODELS

1990 ◽  
Vol 05 (24) ◽  
pp. 4671-4676 ◽  
Author(s):  
ULRICH BLEYER ◽  
HANS-JÜRGEN SCHMIDT
Keyword(s):  
Power Law ◽  
Fourth Order ◽  
Conformal Transformation ◽  
Preceding Paper ◽  
Internal Space ◽  
De Sitter ◽  
Scale Invariant ◽  
Attractor Solution ◽  
Friedmann Cosmological Models ◽  
Kaluza Klein

The conformal relation between scale-invariant fourth-order gravity and Kaluza-Klein models as derived in the preceding paper (I) is applied to Friedmann cosmological models. Especially, the result that power-law inflation is an attractor solution can be carried over, but the conformal transformation brings power-law inflation to de Sitter-like exponential inflation, or power-law inflation a ≈ t. The results depend essentially on the dimension of the internal space.

Generalized Gravity Theory Constrained by CMBR Observations

2005 ◽  
Vol 277-279 ◽  
pp. 795-798
Author(s):  
Hyerim Noh
Keyword(s):  
Gravitational Wave ◽  
Energy Scale ◽  
Gravity Theory ◽  
Coupling Constants ◽  
Spectral Indices ◽  
Cosmological Perturbations ◽  
Scale Invariant ◽  
Inflation Model ◽  
Slow Roll ◽  
Angular Scale

We investigate the cosmological perturbations based on the f(R) gravity theory. Comparing the large angular scale CMBR observation we obtain several important constraints on the inflation model based on the f(R) gravity theory: the ordinary slow-roll assumption during the inflation with the Zel’dovich spectral conditions for the scalar and the tensor-type structures yields R2 gravity as the unique candidate. Also, the considered model predicts the nearly scale-invariant Zel’dovich spectra. We derive the strong constraints on the coupling constants of the R2 term and the energy scale during the inflation using the COBE-DMR observations. The result shows the gravitational wave contribution is very small. Therefore, future observations of the spectral indices and the gravitational wave contribution to CMBR temperature and polarization anisotropies will subject the current inflation models to a test.

scholarly journals ON VACUUM DENSITY, THE INITIAL SINGULARITY AND DARK ENERGY

2009 ◽  
Vol 18 (14) ◽  
pp. 2343-2349 ◽  
Author(s):  
SAULO CARNEIRO ◽  
REZA TAVAKOL
Keyword(s):  
Phase Transition ◽  
Vacuum Energy ◽  
Field Potential ◽  
Scalar Fields ◽  
Vacuum Energy Density ◽  
De Sitter ◽  
Scale Invariant ◽  
Standard Cosmology ◽  
Slow Roll ◽  
Free Fields

Standard cosmology poses a number of important questions. Apart from its singular origin, it possesses early and late accelerating phases required to account for observations. The vacuum energy has been considered as a possible way to resolve some of these questions. The vacuum energy density induced by free fields in an early de Sitter phase has earlier been estimated to be proportional to H4, while more recently it has been suggested that the QCD condensate induces a term proportional to H at late times. These results have been employed in models which are nonsingular and inflationary at early times and accelerating at late times. Here we cast these models in terms of scalar fields and study the corresponding spectrum of primordial perturbations. At early times the spectrum is found to be not scale-invariant, thus implying that slow roll inflation is still required after the phase transition induced by the vacuum. At late times the corresponding scalar field potential is harmonic, with a mass of the order of the Hubble scale — a result that may be understood in the light of the holographic conjecture.

scholarly journals FUBINI VACUA AS A CLASSICAL DE SITTER VACUA

2007 ◽  
Vol 22 (29) ◽  
pp. 2217-2235 ◽  
Author(s):  
F. LORAN
Keyword(s):  
Einstein Field Equation ◽  
Minkowski Spacetime ◽  
Vacuum State ◽  
Information Geometry ◽  
Conformal Group ◽  
De Sitter ◽  
Frw Universe ◽  
Scale Invariant ◽  
Scalar Theory ◽  
De Sitter Vacua

The Fubini's idea to introduce a fundamental scale of hadron phenomena by means of dilatation non-invariant vacuum state in the framework of a scale invariant Lagrangian field theory is recalled. The Fubini vacua is invariant under the de Sitter subgroup of the full conformal group. We obtain a finite entropy for the quantum state corresponding to the classical Fubini vacua in Euclidean spacetime resembling the entropy of the de Sitter vacua. In Minkowski spacetime it is shown that the Fubini vacua is mainly a bath of radiation with Rayleigh–Jeans distribution for the low energy radiation. In four dimensions, the critical scalar theory is shown to be equivalent to the Einstein field equation in the ansatz of conformally flat metrics and to the SU(2) Yang–Mills theory in the 't Hooft ansatz. In D dimensions, the Hitchin formula for the information geometry metric of the moduli space of instantons is used to obtain the information geometry of the free-parameter space of the Fubini vacua which is shown to be a (D+1)-dimensional AdS space. Considering the Fubini vacua as a de Sitter vacua, the corresponding cosmological constant is shown to be given by the coupling constant of the critical scalar theory. In Minkowski spacetime it is shown that the Fubini vacua are equivalent to an open FRW universe.

scholarly journals Low-ℓ CMB from string-scale SUSY breaking?

2016 ◽  
Vol 32 (01) ◽  
pp. 1730001 ◽  
Author(s):  
A. Sagnotti
Keyword(s):  
Cold Dark Matter ◽  
Turning Point ◽  
Power Spectra ◽  
Low Frequency ◽  
Susy Breaking ◽  
Microwave Background ◽  
Scale Invariant ◽  
Slow Roll ◽  
Likelihood Analysis ◽  
Nonlinear Realizations

Models of inflation are instructive playgrounds for supersymmetry (SUSY) breaking in Supergravity and String Theory. In particular, combinations of branes and orientifolds that are not mutually BPS can lead to brane SUSY breaking, a phenomenon where nonlinear realizations are accompanied, in tachyon-free vacua, by the emergence of steep exponential potentials. When combined with milder terms, these exponentials can lead to slow-roll after a fast ascent and a turning point. This leaves behind distinctive patterns of scalar perturbations, where pre-inflationary peaks can lie well apart from an almost scale invariant profile. I review recent attempts to connect these power spectra to the low-[Formula: see text] cosmic microwave background (CMB), and a corresponding one-parameter extension of Lambda cold dark matter ([Formula: see text]CDM) with a low-frequency cut [Formula: see text]. A detailed likelihood analysis led to [Formula: see text], at 99.4% confidence level, in an extended Galactic mask with [Formula: see text], to be compared with a nearby value at 88.5% in the standard Planck 2015 mask with [Formula: see text]. In these scenarios, one would be confronted, in the CMB, with relics of an epoch of deceleration that preceded the onset of slow-roll.

scholarly journals Time dependent couplings as observables in de Sitter space

2014 ◽  
Vol 29 (08) ◽  
pp. 1430016 ◽  
Author(s):  
Hiroyuki Kitamoto ◽  
Yoshihisa Kitazawa
Keyword(s):  
Physical Mechanism ◽  
Quantum Effect ◽  
De Sitter Space ◽  
Time Dependent ◽  
General Covariance ◽  
De Sitter ◽  
Scale Invariant ◽  
Logarithmic Corrections ◽  
Slow Roll ◽  
The One

We summarize and expand our investigations concerning the soft graviton effects on microscopic matter dynamics in de Sitter space. The physical couplings receive IR logarithmic corrections which are sensitive to the IR cutoff at the one-loop level. The scale invariant spectrum in the gravitational propagator at the super-horizon scale is the source of the de Sitter symmetry breaking. The quartic scalar, Yukawa and gauge couplings become time dependent and diminish with time. In contrast, the Newton's constant increases with time. We clarify the physical mechanism behind these effects in terms of the conformal mode dynamics in analogy with 2d quantum gravity. We show that they are the inevitable consequence of the general covariance and lead to gauge invariant predictions. We construct a simple model in which the cosmological constant is self-tuned to vanish due to UV–IR mixing effect. We also discuss phenomenological implications such as decaying Dark Energy and SUSY breaking at the inflation era. The quantum effect alters the classical slow roll picture in general, if the tensor-to-scalar ratio r is as small as 0.01.

scholarly journals An asymptotic method for selection of inflationary modes

2015 ◽  
Vol 30 (09) ◽  
pp. 1550041 ◽  
Author(s):  
E. Yusofi ◽  
M. Mohsenzadeh
Keyword(s):  
General Solution ◽  
Early Universe ◽  
Observational Cosmology ◽  
De Sitter ◽  
Scale Invariant ◽  
Nonlinear Modes ◽  
Sitter Spacetime ◽  
Hankel Functions ◽  
Early Universe Cosmology ◽  
Selection Of

We present some features of early universe cosmology in terms of Hankel functions index (ν). Actually, the recent data from observational cosmology indicate that our universe was nearly de Sitter spacetime in the early times which results in an approximate scale-invariant spectrum. This imposes some constrains on index ν [E. Yusofi and M. Mohsenzadeh, JHEP 09, 020 (2014)]. These constrains stimulate us to use general solution of inflaton field equation for [Formula: see text]. To obtain the general solution for the inflationary background, we use asymptotic expansion of Hankel functions up to nonlinear order of [Formula: see text]. We consider the nonlinear modes as the fundamental modes for early universe during the inflation. In this paper, we obtain the general form of the inflationary modes, scale factor expansion, equation of state and some nonlinear corrections of power spectrum in terms of index ν. These results are general and in quasi-de Sitter and de Sitter limit confirm the conventional results.

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