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.

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 Production of scalar particles in electric field on de Sitter expanding universe

2014 ◽  
Vol 29 (27) ◽  
pp. 1450138 ◽  
Author(s):  
Mihaela-Andreea Băloi
Keyword(s):  
Electric Field ◽  
Particle Production ◽  
Perturbation Methods ◽  
Transition Amplitude ◽  
Scalar Particle ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Scalar Particles ◽  
Sitter Spacetime ◽  
The Universe

The scalar particle production from vacuum in the presence of an electric field, on the de Sitter spacetime is studied. We use perturbation methods to define the transition amplitude. We obtain that the momentum is not conserved in this process. The probability density of pair production is computed by squaring the transition amplitude. Our graphical representations show that, the probability of scalar particle production was important only in the early stages of the universe, when Hubble's constant was very large in comparison with the mass of the particle. Also, we propose here a criterion for particle–antiparticle separation.

scholarly journals The Asymmetric Cosmic Time – The Key to a New Cosmological Model

2020 ◽  
Vol 2 (1) ◽  
pp. 97-111
Author(s):  
Horst Fritsch ◽  
Eberhard Schluecker
Keyword(s):  
Cosmological Model ◽  
Initial Conditions ◽  
Logical Consequence ◽  
Cosmic Time ◽  
Big Bang ◽  
Relativity Theory ◽  
Accelerated Expansion ◽  
Theory Of Relativity ◽  
De Sitter ◽  
The Universe

The asymmetric cosmic time is a logical consequence of the General Theory of Relativity (GR), if one demands that it should apply to the entire cosmos. From the simplest cosmological model that is consistent with the ART (Einstein-de Sitter model) thus follows the < Cosmic Time Hypothesis > (CTH), which offers solutions for many unsolved problems of cosmology that the current standard model of cosmology (ɅCDM model) cannot explain. According to the CTH, space, time and matter form a unit and develop evolutionarily according to identical, time-dependent laws. According to the CTH time has neither beginning nor end. The "big bang" disappears into the infinite past, which is why the universe manages without inflation. The accelerated expansion of the universe is also unlikely to occur if the SN-Ia measurement results are interpreted using the CTH. The cosmological constant Ʌ can then be omitted (Ʌ=0) and consequently no "dark energy" is needed. In addition, the CTH also provides interesting results on the topics: Initial conditions for hypotheses, stability of the expanding, flat universe (Ω=1), cosmic energy balance (is there negative energy ?), theory of earth expansion, unification of natural forces, Mach's principle. Should the CTH receive broad experimental confirmation, the GR could be extended to the "Universal Relativity Theory" (UR).

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.

Massive fermion particle production in de Sitter universe: Ambient space approach

2014 ◽  
Vol 29 (10) ◽  
pp. 1450051 ◽  
Author(s):  
Sepideh Mirabi
Keyword(s):  
Particle Production ◽  
Particle Creation ◽  
Flat Space ◽  
Ambient Space ◽  
Quantum Field ◽  
De Sitter ◽  
Spin Particle ◽  
Massive Spin ◽  
De Sitter Universe ◽  
Space Approach

In this paper, we study the massive spin-½ particle creation in de Sitter (dS) space where the related fields are written in (4+1)-dimensional bulk or the so-called ambient space approach. This approach mimics the flat space quantum field theory (QFT) and the field operators are defined globally on dS space. The main purpose of this study is defining the |in〉 and |out〉 modes for the proposed quantum field which has been written in terms of the dS plane wave in the 4+1 dimensions. We compute, via the Bogoliubov coefficients, the rate of particle creation in dS universe.

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 Interaction between Maxwell field and charged scalar field in de Sitter universe

2015 ◽  
Vol 30 (16) ◽  
pp. 1550088 ◽  
Author(s):  
Cosmin Crucean ◽  
Mihaela-Andreea Băloi
Keyword(s):  
Scalar Field ◽  
Particle Production ◽  
Perturbation Expansion ◽  
Maxwell Field ◽  
De Sitter ◽  
Charged Scalar ◽  
Gravitational Fields ◽  
Sitter Background ◽  
Charged Scalar Field ◽  
De Sitter Universe

We study the theory of interaction between charged scalar field and Maxwell field in de Sitter background. Solving the equation of interacting fields, we define the in–out fields as asymptotic free fields and construct the reduction formalism for scalar field. Then we derive the perturbation expansion of the scattering operator. The first-order transition amplitudes corresponding to particle production from de Sitter vacuum and pair production in an external field are analyzed. We show that all these effects are important only in strong gravitational fields and vanish in the flat limit.

The Large Numbers hypothesis and the Einstein theory of gravitation

1979 ◽  
Vol 365 (1720) ◽  
pp. 19-30 ◽  
Keyword(s):  
Gravitational Theory ◽  
Conclusive Evidence ◽  
De Sitter ◽  
Dimensionless Numbers ◽  
Einstein Theory ◽  
Observable Universe ◽  
Slowing Down ◽  
Large Numbers ◽  
Theory Of Gravitation ◽  
The Universe

A study of the relations between large dimensionless numbers leads one to believe that G , expressed in atomic units, varies with the epoch. The Einstein theory requires G to be constant. One can reconcile these two requirements by supposing that the Einstein theory applies with a metric that differs from the atomic metric. The theory can be developed with conservation of mass by supposing that the continual increase in the mass of the observable universe arises from a continual slowing down of the velocity of recession of the galaxies. One is led to a model of the Universe that was first proposed jointly by Einstein & de Sitter (the E.S. model). The observations of the microwave radiation fit in with this model. The static Schwarzchild metric has to be modified to fit in with the E.S. model for large r . The modification is worked out, and also the motion of planets with the new metric. It is found that there is a difference between ephemeris time and atomic time, and also that there should be an inward spiralling of the planets, referred to atomic units, superposed on the motion given by ordinary gravitational theory. These are effects that can be checked by observation, but there is no conclusive evidence up to the present.

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