The Problem of Flatness of the Universe in the Uncertainty-mediated Inflationary Model

2021 ◽  
Vol 27 (3) ◽  
pp. 302-305
Author(s):  
Yu. V. Dumin
2005 ◽  
Vol 20 (11) ◽  
pp. 2449-2453
Author(s):  
KORAY KARACA ◽  
SELÇUK BAYIN

Assuming that higher dimensions existed in the early stages of the universe where the evolution was inflationary, we construct an open, singularity-free, spatially homogeneous and isotropic cosmological model to study the effects of dimensional reduction that may have taken place during the early stages of the universe. We consider dimensional reduction to take place in a stepwise manner and interpret each step as a phase transition. By imposing suitable boundary conditions we trace their effects on the present day parameters of the universe.


2018 ◽  
Vol 27 (04) ◽  
pp. 1850041 ◽  
Author(s):  
Nasim Saba ◽  
Mehrdad Farhoudi

By studying the chameleon model during inflation, we investigate whether it can be a successful inflationary model, wherein we employ the common typical potential usually used in the literature. Thus, in the context of the slow-roll approximations, we obtain the e-folding number for the model to verify the ability of resolving the problems of standard big bang cosmology. Meanwhile, we apply the constraints on the form of the chosen potential and also on the equation of state parameter coupled to the scalar field. However, the results of the present analysis show that there is not much chance of having the chameleonic inflation. Hence, we suggest that if through some mechanism the chameleon model can be reduced to the standard inflationary model, then it may cover the whole era of the universe from the inflation up to the late time.


1986 ◽  
Vol 01 (02) ◽  
pp. 149-155 ◽  
Author(s):  
B.C. PAUL ◽  
D.P. DATTA ◽  
S. MUKHERJEE

The chaotic inflationary model of the early universe, proposed by Linde is studied within the framework of an anisotropic Kantowski-Sachs cosmology. It is shown that the chaotic model naturally leads to an inflationary phase which also helps in the isotropization of the universe.


2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Milad Solbi ◽  
Kayoomars Karami

AbstractWithin the framework of inflationary model with field-dependent kinetic term for quartic and natural potentials, we investigate generation of the primordial black holes (PBHs) and induced gravitational waves (GWs). In this setup, we consider a kinetic function as $$G(\phi )=g_I(\phi )\big (1+g_{II}(\phi )\big )$$ G ( ϕ ) = g I ( ϕ ) ( 1 + g II ( ϕ ) ) and show that in the presence of first term $$g_I(\phi )$$ g I ( ϕ ) both quartic and natural potentials, in contrast to the standard model of inflation, can be consistent, with the 68% CL of Planck observations. Besides, the second term $$g_{II}(\phi )$$ g II ( ϕ ) can cause a significant enhancement in the primordial curvature perturbations at the small scales which results the PBHs formation. For the both potentials, we obtain an enhancement in the scalar power spectrum at the scales $$k\sim 10^{12}~{\mathrm{Mpc}}^{-1}$$ k ∼ 10 12 Mpc - 1 , $$10^{8}~{\mathrm{Mpc}}^{-1}$$ 10 8 Mpc - 1 , and $$10^{5}~{\mathrm{Mpc}}^{-1}$$ 10 5 Mpc - 1 , which causes PBHs production in mass scales around $$10^{-13}M_{\odot }$$ 10 - 13 M ⊙ , $$10^{-5}M_{\odot }$$ 10 - 5 M ⊙ , and $$10 M_{\odot }$$ 10 M ⊙ , respectively. Observational constraints confirm that PBHs with a mass scale of $$10^{-13}M_{\odot }$$ 10 - 13 M ⊙ can constitute the total of dark matter in the universe. Furthermore, we estimate the energy density parameter of induced GWs which can be examined by the observation. Also we conclude that it can be parametrized as a power-law function $$\Omega _{\mathrm{GW}}\sim (f/f_c)^n$$ Ω GW ∼ ( f / f c ) n , where the power index equals $$n=3-2/\ln (f_c/f)$$ n = 3 - 2 / ln ( f c / f ) in the infrared limit $$f\ll f_{c}$$ f ≪ f c .


2017 ◽  
Vol 26 (03) ◽  
pp. 1750019
Author(s):  
W. S. Hipólito-Ricaldi ◽  
J. R. Villanueva

We enlarge the classes of inflaton and quintessence fields by generalizing the pseudo-Nambu–Goldstone boson potential by means of elliptic Jacobian functions, which are characterized by a parameter [Formula: see text]. We use such a generalization to implement an inflationary era and a late acceleration of the universe. As an inflationary model, the Jacobian generalization leads us to a number of e-foldings and a primordial spectrum of perturbations compatible with the Planck Collaboration 2015. As a quintessence model, a study of the evolution of its equation-of-state (EoS) and its [Formula: see text]–[Formula: see text] plane helps us to classify it as a thawing model. This allows us to consider analytical approximations for the EoS recently discovered for thawing quintessence. By using JLA supernovae Ia and Hubble parameter [Formula: see text] data sets, we perform an observational analysis of the viability of the model as quintessence.


1995 ◽  
Vol 10 (08) ◽  
pp. 1091-1124 ◽  
Author(s):  
PAUL J. STEINHARDT

Observational tests during the next decade may determine if the evolution of the Universe can be understood from fundamental physical principles, or if special initial conditions, coincidences, and new, untestable physical laws must be invoked. The inflationary model of the Universe is an important example of a predictive cosmological theory based on physical principles. In this article, we discuss the distinctive fingerprint that inflation leaves on the cosmic microwave background anisotropy. We then suggest a series of five milestone experimental tests of the microwave background which could determine the validity of the inflationary hypothesis within the next decade.


1988 ◽  
Vol 03 (03) ◽  
pp. 617-629 ◽  
Author(s):  
DAVID H. COULE ◽  
MILAN B. MIJIĆ

We show that in the R2 inflationary model, as in the scalar field case, quantum fluctuations at early times can be sufficiently large that the universe evolves like a random walk. Within this picture we describe the resulting global structure of the universe: the so-called “eternal inflation” scenario. Such behavior can naturally fit into a picture of “quantum creation of the universe”. Inflating domains are present today and in fact are growing in number. Approximately every 10−31 s new hot radiation dominated domains are created which occupy a volume larger than all the previously existing Friedmann universes; during the first ~10−9 fraction of this period the power law expanding volume exceeds the inflating volume. Regularly, numerous domains occur where inflation proceeds purely classically and sufficiently to solve the problems of standard cosmology.


2005 ◽  
Vol 20 (28) ◽  
pp. 6451-6459
Author(s):  
G. GERMÁN ◽  
A. DE LA MACORRA

We construct a two-stage inflationary model which can accommodate early inflation at a scale Λ1 as well as a second stage of inflation at Λ2 with a single scalar field ϕ. We use a symmetric potential, valid in a frictionless world, in which the two inflationary periods have exactly the same scale, i.e. Λ1 = Λ2. However, we see today Λ1 ≫ Λ2 due to the friction terms (expansion of the universe and interaction with matter). These type of models can be motivated from supergravity. Inflation occurs close to the maxima of the potential. As a consequence both inflations are necessarily finite. This opens the interesting possibility that the second inflation has already or is about to end. A first inflation is produced when fluctuations displace the inflaton field from its higher maximum rolling down the potential as in new inflation. Instead of rolling towards a global minimum the inflaton approaches a lower maximum where a second inflation takes place.


2021 ◽  
Vol 41 (1) ◽  
pp. 112-121
Author(s):  
Shomi Aktar ◽  
Anjan Kumar Chowdhury

According to the inflationary model, the universe had a brief period of extraordinarily rapid expansion or inflation during which its diameter increased by a factor at least 1025 times larger than previously thought. In this work an analysis is given on inflationary universe, which expands at a rate intermediate between that of power-law and exponential inflation. We have examined the model of Barrow which is solved exactly and leaded to power law inflation. We have tested a new potential by applying the scalar field using the equation of motion and found some new interior solutions. The Chittagong Univ. J. Sci. 40(1) : 112-121, 2019


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