scholarly journals Vacuum Fluctuations as a Source of Adiabatic Perturbations in Power-Law Inflationary Cosmology

1997 ◽  
Vol 12 (09) ◽  
pp. 647-652 ◽  
Author(s):  
M. Mijić
Keyword(s):  
Power Law ◽  
Quantum Fluctuations ◽  
Inflationary Cosmology ◽  
Vacuum Fluctuations ◽  
Subsequent Evolution ◽  
Density Perturbations ◽  
Inflationary Models

An analysis of the decoherence of quantum fluctuations shows that production of classical adiabatic density perturbations may not take place in models of power-law inflation, a(t)~tp, with 1<p≤ 3. Some consequences for models of extended inflation are pointed out. In general, the condition for decoherence places new constraint on inflationary models, which does not depend on often complicated subsequent evolution.

scholarly journals Quantum Squeezing and Late Time Classical Behavior of Massive Fields in Expanding Robertson–Walker Universe

1997 ◽  
Vol 06 (04) ◽  
pp. 505-514 ◽  
Author(s):  
Milan Mijić
Keyword(s):  
Narrow Range ◽  
Inflationary Cosmology ◽  
Late Time ◽  
Stochastic Evolution ◽  
Vacuum Fluctuations ◽  
Physical Mechanisms ◽  
Density Perturbations ◽  
Picture Analysis ◽  
Classical Behavior ◽  
Classical Evolution

A Schroedinger picture analysis of time dependent quantum oscillators, in a manner of Guth and Pi, clearly identifies two physical mechanisms for possible decoherence of vacuum fluctuations in the early universe: turning of quantum oscillators upside-down, and rapid squeezing of upside-right oscillators so that certain squeezing factor diverges. In inflationary cosmology the former mechanism explains the stochastic evolution of light inflatons and the classical nature of density perturbations in most of the inflationary models, while the later one is responsible for the classical evolution of relatively heavy fields, with masses in a narrow range above the Hubble parameter: [Formula: see text]. The same method may be applied to the study of the decoherence of quantum fluctuations in any Robertson–Walker cosmology.

Inflationary cosmology: First 30+ years

2015 ◽  
Vol 24 (11) ◽  
pp. 1530025 ◽  
Author(s):  
Katsuhiko Sato ◽  
Jun'ichi Yokoyama
Keyword(s):  
Inflationary Cosmology ◽  
Observational Constraints ◽  
Inflation Model ◽  
Common Framework ◽  
Single Field ◽  
The Many ◽  
Historical Developments ◽  
Inflationary Models

Starting with an account of historical developments in Japan and Russia, we review inflationary cosmology and its basic predictions in a pedagogical manner. We also introduce the generalized G-inflation model, in terms of which all the known single-field inflation models may be described. This formalism allows us to analyze and compare the many inflationary models that have been proposed simultaneously and within a common framework. Finally, current observational constraints on inflation are reviewed, with particular emphasis on the sensitivity of the inferred constraints to the choice of datasets used.

Quantum fluctuations and the Casimir effect

2020 ◽  
Vol 29 (08) ◽  
pp. 2050059 ◽  
Author(s):  
Daniel Chemisana ◽  
Jaume Giné ◽  
Jaime Madrid
Keyword(s):  
Spherical Shell ◽  
Uncertainty Principle ◽  
Casimir Effect ◽  
Quantum Fluctuations ◽  
Casimir Energy ◽  
Effective Radius ◽  
Vacuum Fluctuations ◽  
Effective Distance ◽  
Observable Consequence

The most important observable consequence of the vacuum fluctuations is the Casimir effect. Its classical manifestation is a force between two uncharged conductive plates placed a few nanometers apart. In this work, we improve the deduction of the Casimir effect from the uncertainty principle by using an effective radius for the quantum fluctuations. Moreover, the existence of this effective distance is discussed. Finally, a heuristic derivation of the Casimir energy for a spherical shell and a sphere-plate cases is given.

Inflationary cosmology for f(R, ϕ) models with different potentials

2017 ◽  
Vol 95 (11) ◽  
pp. 1074-1085 ◽  
Author(s):  
M. Zubair ◽  
Farzana Kousar
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Energy Density ◽  
Cosmological Constant ◽  
Observational Data ◽  
Power Law ◽  
Early Time ◽  
Inflationary Cosmology ◽  
Effective Equation ◽  
Slow Roll

We examine inflation in [Formula: see text] theory, where a scalar field is coupled to gravity. We have constructed [Formula: see text] models using exponential and power law potentials and study inflation for these models, which can support the early-time acceleration with a useful cosmological constant at high curvature. We have calculated the slow-roll parameters, scalar-to-tensor ratio, and spectral index for these models and analyzed them graphically to check the viability according to recent observational data. We have also presented the evolution of effective equation of state and energy density.

scholarly journals Density perturbations in multifield inflationary models

1998 ◽  
Vol 422 (1-4) ◽  
pp. 52-60 ◽  
Author(s):  
V.F. Mukhanov ◽  
Paul J. Steinhardt
Keyword(s):  
Density Perturbations ◽  
Inflationary Models

scholarly journals Power law plateau inflation potential in the RS II braneworld evading swampland conjecture

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Rathin Adhikari ◽  
Mayukh R. Gangopadhyay ◽  
Yogesh
Keyword(s):  
Power Law ◽  
Correct Choice ◽  
Inflationary Cosmology ◽  
Model Parameters ◽  
De Sitter ◽  
Warm Inflation ◽  
Formula One ◽  
Existential Crisis ◽  
Standard Scenario ◽  
Single Field

AbstractIn the recent time, inflationary cosmology is facing an existential crisis due to the proposed Swampland criterion which aims to evade any (meta-)stable de Sitter construction within the String landscape. It is been realised that a single field slow roll inflation is inconsistent with the Swampland criterion unless the inflationary model is realised in some non-standard scenario such as Warm inflation or the Braneworld scenario. Dimopoulos and Owen (Phys Rev D 94(6): 063518, 2016) introduced a new class of model of inflation dubbed as the power law plateau inflation in the standard cold inflationary scenario. But to realise this model in the standard scenario consistent with observation, they had to introduce a phase of thermal inflation. In this paper we have analysed this model in the braneworld scenario to show that for some choice of the parameters defining the model class, one can have an observationally consistent power law plateau without any phase of thermal inflation. We have also shown that, for the correct choice of model parameters, one can easily satisfy the Swampland criterion. Besides, for correct choice of equation of states ($$w_{re}$$ w re ), one can also satisfy the recently proposed Trans–Planckian Censorship Conjecture (TCC).

CLASSICAL PERTURBATIONS FROM DECOHERENCE OF QUANTUM FLUCTUATIONS IN THE INFLATIONARY UNIVERSE

1990 ◽  
Vol 05 (28) ◽  
pp. 2311-2317 ◽  
Author(s):  
ROBERT BRANDENBERGER ◽  
RAYMOND LAFLAMME ◽  
MILAN MIJIĆ
Keyword(s):  
Scalar Field ◽  
Coherence Length ◽  
Quantum Fluctuations ◽  
Inflationary Universe ◽  
De Sitter ◽  
Density Perturbations ◽  
Hubble Radius ◽  
Universe Models

The evolution of a scalar field interacting with an environment in the de Sitter phase of an inflationary Universe is studied. The environment is taken to be a second scalar field. It is shown that the coherence length of the quantum fluctuations rapidly decreases after the wavelength of the perturbation crosses the Hubble radius. Hence, the fluctuations can be interpreted as classical. This lends support to the usual derivation of the spectrum of density perturbations in inflationary Universe models.

Inflation with non-minimally derivative coupling

2015 ◽  
Vol 30 (28n29) ◽  
pp. 1545004 ◽  
Author(s):  
Nan Yang ◽  
Qing Gao ◽  
Yungui Gong
Keyword(s):  
Gravitational Waves ◽  
Power Law ◽  
Second Order ◽  
Order Correction ◽  
Observational Constraint ◽  
Derivative Coupling ◽  
Primordial Gravitational Waves ◽  
Inflationary Models

We derive the second order correction to the scalar and tensor spectral tilts for the inflationary models with non-minimally derivative coupling. In the high friction limit, the quartic power law potential is consistent with the observational constraint at 95% CL because the amplitude of the primordial gravitational waves is smaller, and the inflaton excursion is sub-Planckian.

scholarly journals CHAOS AND A RESONANCE MECHANISM FOR STRUCTURE FORMATION IN INFLATIONARY MODELS

1998 ◽  
Vol 13 (23) ◽  
pp. 1881-1886 ◽  
Author(s):  
H. P. DE OLIVEIRA ◽  
I. DAMIÃO SOARES
Keyword(s):  
Wave Number ◽  
Minimal Set ◽  
Resonance Mechanism ◽  
Cylindrical Structure ◽  
Scale Functions ◽  
Exponential Expansion ◽  
Effective Cosmological Constant ◽  
Density Perturbations ◽  
The Universe ◽  
Inflationary Models

We exhibit a resonance mechanism of amplification of density perturbations in inflationary models, using a minimal set of ingredients (an effective cosmological constant, a scalar field minimally coupled to the gravitational field and matter), common to most models in the literature of inflation. This mechanism is based on the structure of homoclinic cylinders, emanating from an unstable periodic orbit in the neighborhood of a saddle-center critical point, present in the phase space of the model. The cylindrical structure induces oscillatory motions of the scales of the universe whenever the orbit visits the neighborhood of the saddle-center, before the universe enters a period of exponential expansion. The oscillations of the scale functions produce, by a resonance mechanism, the amplification of a selected wave number spectrum of density perturbations, and can be used to explain the hierarchy of scales observed in the actual universe. The transversal crossings of the homoclinic cylinders induce chaos in the dynamics of the model — a fact closely connected to the resonance mechanism occuring immediately before the exit to inflation.

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