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.

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.

scholarly journals A New Inflationary Universe Scenario with Inhomogeneous Quantum Vacuum

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Yilin Chen ◽  
Jin Wang
Keyword(s):  
Green’S Function ◽  
Potential Barrier ◽  
Green's Function ◽  
Inflationary Universe ◽  
Quantum Vacuum ◽  
Vacuum Fluctuations ◽  
Inflationary Scenario ◽  
Slowing Down ◽  
The Universe ◽  
Inhomogeneous Quantum

We investigate the quantum vacuum and find that the fluctuations can lead to the inhomogeneous quantum vacuum. We find that the vacuum fluctuations can significantly influence the cosmological inhomogeneity, which is different from what was previously expected. By introducing the modified Green’s function, we reach a new inflationary scenario which can explain why the Universe is still expanding without slowing down. We also calculate the tunneling amplitude of the Universe based on the inhomogeneous vacuum. We find that the inhomogeneity can lead to the penetration of the Universe over the potential barrier faster than previously thought.

Generalization of the Gross–Pitaevskii equation for multi-particle cases

2021 ◽  
Author(s):  
Nicolai Bogoliubov ◽  
Mukhayo Rasulova ◽  
Tohir Akramov
Keyword(s):  
Quantum System ◽  
Infinite Number ◽  
Kinetic Equations ◽  
Pair Potential ◽  
Delta Function ◽  
Dirac Delta Function ◽  
New Method ◽  
Pitaevskii Equation ◽  
Dirac Delta ◽  
Special Pair

A new method is proposed to obtain Gross–Pitaevskii equation by the chain of Bogoliubov–Born–Green–Kirkwood–Yvon (BBGKY) quantum kinetic equations. In that sense, we investigate the dynamics of a quantum system including infinite number of identical particles which interact via a (special) pair potential on the form of Dirac delta-function.

scholarly journals Inflationary universe models and clustering of quasar red shifts

1986 ◽  
Vol 119 ◽  
pp. 509-510
Author(s):  
C. Sivaram
Keyword(s):  
Cosmological Model ◽  
Early Universe ◽  
Hubble Constant ◽  
Matter Density ◽  
Inflationary Universe ◽  
Expansion Phase ◽  
Exponential Expansion ◽  
The Universe ◽  
Inflationary Models ◽  
Universe Models

Recently it has been shown that many of the puzzling features of conventional cosmological models (such as the horizon and flatness problems) could be explained by invoking inflationary models of the early universe with an exponential expansion phase at very early epochs. These models have the added advantage that they are able to make a definite prediction about the present matter density in the universe, i.e. they require that the density be exactly equal to the closure density which in turn can be easily estimated from the Hubble constant now known to within a factor of two. Now if one goes back to an earlier idea that explored the possibility of unusual clustering of quasar redshifts around z = 2 or 3, we get an example of another cosmological model with a definite prediction for the present overall matter density. This is a modified version of the Eddington-Lemaitre type of model which naturally accommodates such features as a clustering of quasars at certain epochs. From these models one can get a prediction for the present matter density which would be an involved function of the Hubble constant and the redshifts at which such clustering occurs. It can be shown that if such clustering had occurred at any z, the present matter density predicted would be substantially smaller than the corresponding closure density. The conclusion is that any clustering of quasar redshifts is incompatiable with inflationary universe models, indirectly providing observational support for these new theories.

scholarly journals Some Critical Remarks on the Inflationary Universe Concept

1988 ◽  
Vol 130 ◽  
pp. 63-65
Author(s):  
Gerhard Börner
Keyword(s):  
Large Scale ◽  
Higgs Field ◽  
Quantitative Model ◽  
Time Interval ◽  
Inflationary Universe ◽  
Fundamental Particle ◽  
The Standard Model ◽  
History Of ◽  
Simple Change ◽  
The Universe

The basic idea of inflation in cosmology is very simple: It is the assumption that the expansion factor R(t) of a Friedmann-Lemaltre cosmological model grows exponentially during a brief time interval in the very early universe. The phase of exponential growth is followed by a thermalizatlon stage and a subsequent “normal” evolution R(t)∼vt. This “Inflationary expansion“ can help to solve cosmological puzzles inherent in the standard model - such as the large-scale flatness, the horizon structure, the numerical value of the entropy in a comoving volume [for a review see Brandenberger 1985]. To turn this romantic idea of inflation into a quantitative model requires still a lot of work: The simple change in the thermal history of the universe must be derived from a fundamental particle theory. The models proposed so far do not inspire much confidence. In the following a few difficulties of the Higgs field idea, especially the Coleman-Weinberg formalism will be pointed out (section 1). In section 2 some problems connected with the investigation of initially strongly anisotropic or Inhomogeneous cosmological models will be mentioned.

BACKSCATTERING AND THE DECAY OF TRANSMITTANCE IN A COHERENTLY ABSORBING OR AMPLIFYING ORDERED CHAIN

1996 ◽  
Vol 10 (03n05) ◽  
pp. 125-132 ◽  
Author(s):  
ASOK K. SEN
Keyword(s):  
Quantum System ◽  
Electronic Properties ◽  
Recent Work ◽  
Active Medium ◽  
Open Quantum System ◽  
Tight Binding ◽  
One Dimensional ◽  
A Value ◽  
Closed Quantum System ◽  
Coherent Amplification

We study electronic properties of a one-dimensional, semi-infinite ordered chain in the presence of either absorption or amplification at each site (the site potentials having imaginary positive or negative parts) within a single-band, tight binding Hamiltonian. The spectrum in either case for an isolated (closed) quantum system becomes broader compared to the regular Bloch case. For an infinitely long ordered chain (open quantum system), the reflectance saturates to a value greater (lesser) than unity in the amplifying (absorbing) case and the transmittance decays to zero in either case. Thus, in contrast to a recent work of Pradhan and Kumar [Phys. Rev.B50, 9644 (1994)], it is not necessary to have any “synergy between wave confinement” due to any disorder or interaction induced confining mechanism on the transmitted wave and “coherent amplification by the active medium” to achieve an amplification in the reflectance.

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

BARYOGENESIS IN THE INFLATIONARY UNIVERSE —THE INSTANTANEOUS REHEATING MODEL—

1987 ◽  
Vol 02 (06) ◽  
pp. 1809-1828 ◽  
Author(s):  
JUN’ICHI YOKOYAMA ◽  
HIDEO KODAMA ◽  
KATSUHIKO SATO ◽  
NOBUAKI SATO
Keyword(s):  
Thermal Equilibrium ◽  
Large Scale ◽  
Baryon Asymmetry ◽  
Higgs Bosons ◽  
Boson Mass ◽  
Inflationary Universe ◽  
Higgs Boson Mass ◽  
Boltzmann Equations ◽  
Thermal Equilibrium State ◽  
The Universe

Baryogenesis in the inflationary universe is investigated, assuming that the universe is reheated instantaneously. Boltzmann equations are numerically integrated to trace time evolution of asymmetries in quarks and leptons in the Friedmann stage after the reheating, starting from the thermal equilibrium state. It is shown that the sign of the final baryon asymmetry may change depending on the reheating temperature as a result of interplay of superheavy gauge and Higgs bosons, and its mechanism is clarified. Furthermore we suggest a mechanism of generating isocurvature fluctuations which could be the origin of the large scale structure of the universe. It is also found in the instantaneous reheating model that the reheating temperature Ti must satisfy Ti>MH/10 (MH: Higgs boson mass) for the observed baryon/entropy ratio to be explained.

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