Cosmological perturbations in the inflationary Universe

1997 ◽  
Vol 56 (6) ◽  
pp. 3357-3364 ◽  
Author(s):  
Winfried Zimdahl
Keyword(s):  
Inflationary Universe ◽  
Cosmological Perturbations

Cosmological perturbations in the inflationary universe

1987 ◽  
Vol 193 (4) ◽  
pp. 427-432 ◽  
Author(s):  
V.F. Mukhanov ◽  
L.A. Kofman ◽  
D.Yu. Pogosyan
Keyword(s):  
Inflationary Universe ◽  
Cosmological Perturbations

scholarly journals ON SIGNATURES OF SHORT DISTANCE PHYSICS IN THE COSMIC MICROWAVE BACKGROUND

2002 ◽  
Vol 17 (25) ◽  
pp. 3663-3680 ◽  
Author(s):  
ROBERT H. BRANDENBERGER ◽  
JÉRÔME MARTIN
Keyword(s):  
Excited State ◽  
Cosmic Microwave Background ◽  
Short Distance ◽  
The State ◽  
Inflationary Universe ◽  
Late Time ◽  
Cosmological Perturbations ◽  
Microwave Background ◽  
Hubble Radius

Following a self-contained review of the basics of the theory of cosmological perturbations, we discuss why the conclusions reached in the recent paper by Kaloper et al.1 are too pessimistic estimates of the amplitude of possible imprints of trans-Planckian (string) physics on the spectrum of cosmic microwave anisotropies in an inflationary universe. It is shown that the likely origin of large trans-Planckian effects on late time cosmological fluctuations comes from nonadiabatic evolution of the state of fluctuations while the wavelength is smaller than the Planck (string) scale, resulting in an excited state at the time that the wavelength crosses the Hubble radius during inflation.

scholarly journals R2-Corrections to Chaotic Inflation

2003 ◽  
Vol 18 (29) ◽  
pp. 2039-2049 ◽  
Author(s):  
Víctor H. Cárdenas ◽  
Sergio del Campo ◽  
Ramón Herrera
Keyword(s):  
Early Evolution ◽  
Inflationary Universe ◽  
Universe Model ◽  
Spectral Indices ◽  
Cosmological Perturbations ◽  
Evolution Of The Universe ◽  
Scalar Density ◽  
Higher Derivative ◽  
Derivative Term ◽  
The Universe

Scalar density cosmological perturbations, spectral indices and reheating in a chaotic inflationary universe model, in which a higher derivative term is added, are investigated. This term is supposed to play an important role in the early evolution of the Universe, specifically at times closer to the Planck era.

Cosmological perturbations in inflationary-universe models

1984 ◽  
Vol 29 (10) ◽  
pp. 2172-2190 ◽  
Author(s):  
Robert Brandenberger ◽  
Ronald Kahn
Keyword(s):  
Inflationary Universe ◽  
Cosmological Perturbations ◽  
Universe Models

scholarly journals No Intrinsic Decoherence of Inflationary Cosmological Perturbations

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 27
Author(s):  
Jen-Tsung Hsiang ◽  
Bei-Lok Hu
Keyword(s):  
Quantum System ◽  
Wigner Function ◽  
Semiclassical Limit ◽  
Delta Function ◽  
Quantum Decoherence ◽  
Inflationary Universe ◽  
Cosmological Perturbations ◽  
Intrinsic Decoherence ◽  
Closed Quantum System ◽  
The Universe

After a brief summary of the four main veins in the treatment of decoherence and quantum to classical transition in cosmology since the 1980s, we focus on one of these veins in the study of quantum decoherence of cosmological perturbations in inflationary universe, the case when it does not rely on any environment. This is what ‘intrinsic’ in the title refers to—a closed quantum system, consisting of a quantum field which drives inflation. The question is whether its quantum perturbations, which interact with the density contrast giving rise to structures in the universe, decohere with an inflationary expansion of the universe. A dominant view which had propagated for a quarter of a century asserts yes, based on the belief that the large squeezing of a quantum state after a duration of inflation renders the system effectively classical. This paper debunks this view by identifying the technical fault-lines in its derivations and revealing the pitfalls in its arguments which drew earlier authors to this wrong conclusion. We use a few simple quantum mechanical models to expound where the fallacy originated: The highly squeezed ellipse quadrature in phase space cannot be simplified to a line, and the Wigner function cannot be replaced by a delta function. These measures amount to taking only the leading order in the relevant parameters in seeking the semiclassical limit and ignoring the subdominant contributions where quantum features reside. Doing so violates the bounds of the Wigner function, and its wave functions possess negative eigenvalues. Moreover, the Robertson-Schrödinger uncertainty relation for a pure state is violated. For inflationary cosmological perturbations, in addition to these features, entanglement exists between the created pairs. This uniquely quantum feature cannot be easily argued away. Indeed, it could be our best hope to retroduce the quantum nature of cosmological perturbations and the trace of an inflation field. All this points to the invariant fact that a closed quantum system, even when highly squeezed, evolves unitarily without loss of coherence; quantum cosmological perturbations do not decohere by themselves.

Sign in / Sign up

Export Citation Format

Share Document