scholarly journals Emergent classical universes from initial quantum states in a tomographical description

2020 ◽  
Vol 17 (11) ◽  
pp. 2050167
Author(s):  
Cosimo Stornaiolo
Keyword(s):  
Necessary Conditions ◽  
Phenomenological Approach ◽  
De Sitter ◽  
Present Value ◽  
Asymptotic Expressions ◽  
Classical Transition ◽  
Quantum Tomograms ◽  
De Sitter Universe ◽  
The Universe ◽  
Extract Information

Quantum and classical physical states are represented in a unified way when they aredescribed by symplectic tomography. Therefore this representation allows us to study directly the necessary conditions for a classical universe to emerge from a quantum state. In a previous work on the de Sitter universe this was done by comparing the classical limit of the quantum tomograms with those resulting from the classical cosmological equations. In this paper, we first review these results and extend them to all the de Sitter models. We show further that these tomograms can be obtained directly from transposing the Wheeler–De Witt equation to the tomographic variables. Subsequently, because the classic limits of the quantum tomograms are identified with their asymptotic expressions, we find the necessary conditions to extend the previous results by taking the tomograms of the WKB solutions of the Wheeler–DeWitt equation with an any potential. Furthermore, in the previous works, we found that the de Sitter models undergo the quantum-to-classical transition when the cosmological constant decays to its present value, we discuss at the end how far we can extend this result to more general models. In the conclusions, after discussing any improvements and developments of the results of this work, we sketch a phenomenological approach from which to extract information about the initial states of the universe.

scholarly journals WE PROBABLY LIVE ON AN INFLATING BRANE-WORLD

2011 ◽  
Vol 20 (14) ◽  
pp. 2809-2816
Author(s):  
ISHWAREE P. NEUPANE
Keyword(s):  
Zero Mode ◽  
De Sitter Space ◽  
Brane World ◽  
Conformal Field Theories ◽  
De Sitter ◽  
Conformal Field ◽  
Sitter Spacetime ◽  
Acceleration Of The Universe ◽  
De Sitter Universe ◽  
The Universe

Brane-world models, where observers are trapped within the thickness of a 3-brane, offer novel perspectives on gravitation and cosmology. In this essay, it is argued that the problem of a late epoch acceleration of the universe is well explained in the framework of a 4-dimensional de Sitter universe embedded in a 5-dimensional de Sitter spacetime. While a 5-dimensional Anti-de Sitter space background is important for studying conformal field theories for its role in the AdS/CFT correspondence, the existence of a 5-dimensional de Sitter space is crucial for finding an effective 4-dimensional Newton constant that remains finite and a normalizable zero-mode graviton wave function.

scholarly journals THE RETURN OF A STATIC UNIVERSE AND THE END OF COSMOLOGY

2008 ◽  
Vol 17 (03n04) ◽  
pp. 685-690 ◽  
Author(s):  
LAWRENCE M. KRAUSS ◽  
ROBERT J. SCHERRER
Keyword(s):  
Coordinate System ◽  
Vacuum Energy ◽  
Big Bang ◽  
Light Elements ◽  
De Sitter ◽  
True Nature ◽  
Static Universe ◽  
Hubble Expansion ◽  
De Sitter Universe ◽  
The Universe

We demonstrate that as we extrapolate the current ΛCDM universe forward in time, all evidence of the Hubble expansion will disappear, so that observers in our "island universe" will be fundamentally incapable of determining the true nature of the universe, including the existence of the highly dominant vacuum energy, the existence of the CMB, and the primordial origin of light elements. With these pillars of the modern Big Bang gone, this epoch will mark the end of cosmology and the return of a static universe. In this sense, the coordinate system appropriate for future observers will perhaps fittingly resemble the static coordinate system in which the de Sitter universe was first presented.

scholarly journals Dynamics in Interacting Scalar-Torsion Cosmology

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 244
Author(s):  
Andronikos Paliathanasis
Keyword(s):  
Special Interest ◽  
System Analysis ◽  
Stable Solution ◽  
Gravitational Theory ◽  
De Sitter ◽  
Dark Sector ◽  
Background Space ◽  
Qualitative Evolution ◽  
De Sitter Universe ◽  
The Universe

In a spatially flat Friedmann–Lemaître–Robertson–Walker background space, we consider a scalar-torsion gravitational model which has similar properties to the dilaton theory. This teleparallel model is invariant under a discrete transformation similar to the Gasperini–Veneziano duality transformation. Moreover, in the gravitational action integral, we introduce the Lagrangian function of a pressureless fluid source which is coupled to the teleparallel dilaton field. This specific gravitational theory with interaction in the dark sector of the universe was investigated by using methods of the dynamical system analysis. We calculate that the theory provides various areas of special interest for the evolution of the cosmological history. Inflationary scaling solutions and the de Sitter universe are recovered. Furthermore, we calculate that there exist an attractor which provides a stable solution where the two fluid components, the scalar field and the pressureless matter, contribute in the cosmological fluid. This solution is of special interest because it can describe the present epoch. Finally, the qualitative evolution of the cosmographic parameters is discussed.

scholarly journals Does holographic equipartition demand a pure cosmological constant?

2020 ◽  
pp. 2050334
Author(s):  
P. B. Krishna ◽  
Titus K. Mathew
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Dark Energy Model ◽  
State Parameter ◽  
De Sitter ◽  
Entropy Maximization ◽  
Expansion Of The Universe ◽  
The Law ◽  
De Sitter Universe ◽  
The Universe

The spacial expansion of the universe could be described as a tendency for satisfying holographic equipartition which inevitably demands the presence of dark energy. We explore whether this novel idea proposed by Padmanabhan gives any additional insights into the nature of dark energy. In particular, we obtain the constraints imposed by the law of emergence on the equation of state parameter, [Formula: see text]. We also present a thermodynamic motivation for the obtained constraints on [Formula: see text]. Further, we explicitly prove the feasibility of describing a dynamic dark energy model through the law of emergence. Interestingly, both holographic equipartition and the entropy maximization demand an asymptotically de Sitter universe with [Formula: see text], rather than a pure cosmological constant.

scholarly journals Evolution of Inhomogeneities in the Inflationary Universe -No Hair Theorem or Multi-Production of Universes?-

1988 ◽  
Vol 130 ◽  
pp. 67-75
Author(s):  
Katsuhiko Sato
Keyword(s):  
Critical Length ◽  
High Density ◽  
Density Contrast ◽  
Inflationary Universe ◽  
De Sitter ◽  
Inhomogeneous Universe ◽  
Sitter Universe ◽  
De Sitter Universe ◽  
The Universe

Recent investigations on the evolution of the inhomogeneities in the inflationary universe are reviewed. 1) Strict cosmological no hair theorem does not hold, but the class of inhomogeneous universe which evolve to homogeneous de Sitter universe is finite, i.e, “weak cosmic no hair theorem” holds. 2) High density regions in the inhomogeneous universe evolve to wormholes provided that i) the size of the regions is greater than the horizon length, but smaller than a critical length which is the function of the density contrast, and ii) the density is three times higher than that of surrounding region. 3) If wormholes are formed copiously in the period of inflation, they evolve to causally disconnected “child- universes”. In this scenario, the universe we are now observing is one of the locally flat regions.

De Sitter and bounce solutions from anisotropy in extended gravity cosmology

2019 ◽  
Vol 34 (39) ◽  
pp. 1950321 ◽  
Author(s):  
B. Mishra ◽  
G. Ribeiro ◽  
P. H. R. S. Moraes
Keyword(s):  
Big Bang ◽  
Late Time ◽  
Type I ◽  
De Sitter ◽  
Field Equations ◽  
Extended Gravity ◽  
Numerical Fitting ◽  
De Sitter Universe ◽  
The Big Bang ◽  
The Universe

We investigate the consequences of incepting the Bianchi type I metric in the [Formula: see text] gravity theory field equations. We particularly derive solutions for a matter-dominated universe. From such a scenario, it is possible to predict a late-time de Sitter universe. Moreover, depending on the numerical fitting function for the scale factor, the universe is predicted to bounce and evade the Big Bang singularity.

Vacuum expansion in arbitrary–gauge Lyra geometry

2014 ◽  
Vol 92 (4) ◽  
pp. 311-315 ◽  
Author(s):  
Hoavo Hova
Keyword(s):  
Lyra Geometry ◽  
Cosmological Term ◽  
Accelerated Expansion ◽  
Time Varying ◽  
De Sitter ◽  
Lyra’S Geometry ◽  
De Sitter Universe ◽  
The Universe ◽  
Matter Fields ◽  
Arbitrary Gauge

We propose a cosmological model containing a cosmological term in arbitrary gauge in Lyra’s geometry. In the absence of matter fields (such as radiation or baryonic), a constant cosmological term does not lead to the de Sitter universe as it is seen in Riemannian geometry, while a time-varying cosmological term can drive the universe into an accelerated expansion.

scholarly journals New quantum phase of the Universe before inflation and its cosmological and dark energy implications

2019 ◽  
Vol 34 (27) ◽  
pp. 1950155
Author(s):  
Norma G. Sanchez
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Quantum Physics ◽  
Planck Scale ◽  
De Sitter ◽  
Quantum Domain ◽  
Wave Particle Duality ◽  
Classical Quantum ◽  
De Sitter Universe ◽  
The Universe

The physical history of the Universe is completed by including the quantum Planckian and trans-Planckian phase before inflation in the Standard Model of the Universe in agreement with observations. In the absence of a complete quantum theory of gravity, we start from quantum physics and its foundational milestone. The universal classical-quantum (or wave-particle) duality, which we extend to gravity and the Planck domain. As a consequence, classical, quantum Planckian and super-Planckian regimes are covered, and the usual quantum domain as well. A new quantum precursor phase of the Universe appears beyond the Planck scale [Formula: see text]: [Formula: see text]; the known classical/semiclassical Universe being in the range: [Formula: see text]. We extend in this way the de Sitter Universe to the quantum domain: classical-quantum de Sitter duality. As a result: (i) The classical and quantum dual de Sitter temperatures and entropies are naturally included, and the different (classical, semiclassical, quantum Planckian and trans-Planckian) de Sitter regimes characterized in a precise and unifying way. (ii) We apply it to relevant cosmological examples as the CMB, inflation and dark energy. This allows us to find in a simple and consistent way. (iii) Full quantum inflationary spectra and their CMB observables, including in particular the classical known inflation spectra and the quantum corrections to them. (iv) A whole unifying picture for the Universe epochs and their quantum precursors emerges with the cosmological constant as the vacuum energy, entropy and temperature of the Universe, clarifying the so-called cosmological constant problem which once more in its rich history needed to be revised.

scholarly journals Gauss–Bonnet modified gravity models with bouncing behavior

2016 ◽  
Vol 31 (17) ◽  
pp. 1650108 ◽  
Author(s):  
Anna Escofet ◽  
Emilio Elizalde
Keyword(s):  
Modified Gravity ◽  
Physical Nature ◽  
Gravity Models ◽  
Accelerated Expansion ◽  
De Sitter ◽  
Eos Parameter ◽  
Energy Models ◽  
De Sitter Universe ◽  
The Universe ◽  
Modified Gravity Models

The following issue is addressed: How the addition of a Gauss–Bonnet term (generically coming from most fundamental theories, as string and M theories), to a viable model, can change the specific properties, and even the physical nature, of the corresponding cosmological solutions? Specifically, brand new original dark energy models are obtained in this way with quite interesting properties, which exhibit, in a unified fashion, the three distinguished possible cosmological phases corresponding to phantom matter, quintessence and ordinary matter, respectively. A model, in which the equation of state (EoS) parameter, w, is a function of time, is seen to lead either to a singularity of the Big Rip kind or to a bouncing solution which evolves into a de Sitter universe with w = −1. Moreover, new Gauss–Bonnet modified gravity models with bouncing behavior in the early stages of the universe evolution are obtained and tested for the validity and stability of the corresponding solutions. They allow for a remarkably natural, unified description of a bouncing behavior at early times and accelerated expansion at present.

Mapping between different cosmological eras in scale-covariant formalism

2020 ◽  
Vol 35 (07) ◽  
pp. 2050044
Author(s):  
Marlos O. Ribas ◽  
Fernando P. Devecchi ◽  
Gilberto M. Kremer
Keyword(s):  
Particle Production ◽  
Direct Consequence ◽  
Einstein Equations ◽  
Relativity Theory ◽  
De Sitter ◽  
Covariant Formalism ◽  
Large Numbers ◽  
New Equation ◽  
De Sitter Universe ◽  
The Universe

In this work we consider the scale-covariant formalism proposed by Canuto et al.,[Formula: see text] in order to map different eras of the universe. This technique considers a scale gauge function that can be adjusted by using different arguments like Dirac’s large numbers hypothesis or a restriction on the particle production rate. A Chaplygin constituent shows to be a consistent idea to establish a mapping between an old decelerated–accelerated universe ruled by Einstein equations and an early universe, where a new equation of state appears together with a modified general relativity theory and a de Sitter universe then emerges. These properties are a direct consequence of the use of the scale-covariant formalism. Besides, a new discussion and remarks are presented related to the well-known barotropic constituent case.

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