Ground state of the universe in quantum cosmology

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641014 ◽  
Author(s):  
Natalia Gorobey ◽  
Alexander Lukyanenko
Keyword(s):  
Quantum Gravity ◽  
Ground State ◽  
Quantum Dynamics ◽  
Homogeneous Model ◽  
Cosmic Time ◽  
Matter Content ◽  
Closed Universe ◽  
Initial State ◽  
Covariant Quantum ◽  
The Universe

We find a physical state of a closed universe with the minimal excitation of the universe expansion energy in quantum gravity. It is an analog of the vacuum state of the ordinary quantum field theory in the Minkowsky space, but in our approach an energy of space of a closed universe together with the energy of its matter content are minimized. This ground state is chosen among an enlarged set of physical states, compared with the ordinary covariant quantum gravity. In our approach, physical states are determined by weak constraints: quantum mechanical averages of gravitational constraint operators equal zero. As a result, they appear to be non-static in such a modification of quantum gravity. Quantum dynamics of the universe is described by Schrödinger equation with a cosmic time determined by weak gravitational constraints. In order to obtain the observed megascopic universe with the inflation stage just after its quantum beginning, a lot of the energy in the form of the inflaton scalar field condensate is prescribed to the initial state. Parameters of the initial state for a homogeneous model of the universe are calculated.

“Stationary” Schrödinger equation in quantum cosmology

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040040
Author(s):  
N. Gorobey ◽  
A. Lukyanenko ◽  
A. Shavrin
Keyword(s):  
Energy Density ◽  
Quantum Cosmology ◽  
Quantum Dynamics ◽  
Harmonic Approximation ◽  
Cosmic Time ◽  
Positive Functional ◽  
The Universe ◽  
Principle Of Extremum ◽  
Extremum Conditions

The conditional principle of extremum in quantum cosmology is formulated for a positive functional of the energy density of space, in which gravitational constraints serve as additional conditions. The extremum conditions determine the discrete spectrum of the “stationary” state of the universe with the corresponding values of the energy density of space. A dynamic interpretation of solutions is proposed, in which the quantum number of the energy density plays the role of cosmic time. In the self-consistent harmonic approximation, the quantum dynamics of the anisotropic model of the Bianchi IX universe is considered.

scholarly journals THE ENTROPY GAP AND THE TIME ASYMMETRY

1996 ◽  
Vol 11 (09) ◽  
pp. 755-762 ◽  
Author(s):  
ROBERTO AQUILANO ◽  
MARIO CASTAGNINO
Keyword(s):  
Observational Data ◽  
Homogeneous Model ◽  
Initial State ◽  
Time Asymmetry ◽  
Universe Expansion ◽  
Low Entropy ◽  
The Universe

The universe time asymmetry is essentially produced by its low-entropy unstable initial state. Using quantitative arguments P. Davies2 has demonstrated that the universe expansion may produce a decreasing of entropy and, therefore, this fact explains its low-entropy states. This idea is implemented in a qualitative way in a simple homogeneous model. A rough coincidence with observational data is found.

THREE-DIMENSIONAL QUANTUM GRAVITY AS DYNAMICAL TRIANGULATION

1991 ◽  
Vol 06 (20) ◽  
pp. 1863-1884 ◽  
Author(s):  
M. E. AGISHTEIN ◽  
A. A. MIGDAL
Keyword(s):  
Quantum Gravity ◽  
Three Dimensional ◽  
Critical Value ◽  
Two Dimensions ◽  
Geodesic Sphere ◽  
Closed Universe ◽  
3 Dimensional ◽  
Average Curvature ◽  
Dynamical Triangulation ◽  
The Universe

The dynamical triangulation model of 3-dimensional Quantum Gravity is defined and studied. We propose two different algorithms for numerical simulations, leading to consistent results. One is the 3-dimensional generalization of the bonds flip, another is more sophisticated algorithm, based on Schwinger–Dyson equations. We found such care necessary, because our results appear to be quite unexpected. We simulated up to 60000 tetrahedra and observed none of the feared pathologies like factorial growth of the partition function with volume, or collapse to the branched polymer phase. The volume of the Universe grows exponentially when the bare cosmological constant λ approaches the critical value λ c from above, but the closed Universe exists and has peculiar continuum limit. The Universe compressibility diverges as (λ − λ c )−2 and the bare Newton constant linearly approaches negative critical value as λ goes to λ c , provided the average curvature is kept at zero. The fractal properties turned out to be the same, as in two dimensions, namely the effective Hausdorff dimension grows logarithmically with the size of the test geodesic sphere.

Cosmological spacetimes

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Cosmological Model ◽  
Large Scale ◽  
Cosmic Time ◽  
De Sitter ◽  
Matter Distribution ◽  
Observable Universe ◽  
Cosmological Principle ◽  
Riemannian Spacetime ◽  
The Universe ◽  
Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

Naming the Big Bang

2012 ◽  
Vol 44 (1) ◽  
pp. 3-36 ◽  
Author(s):  
Helge Kragh
Keyword(s):  
Scientific Community ◽  
Big Bang ◽  
Consensus Model ◽  
Initial State ◽  
The Standard Model ◽  
Modern Cosmology ◽  
Fred Hoyle ◽  
The Big Bang ◽  
The Universe ◽  
Origin Of The Universe

The standard model of modern cosmology is known as the hot big bang, a name that refers to the initial state of the universe some fourteen billion years ago. The name Big Bang introduced by Fred Hoyle in 1949 is one of the most successful scientific neologisms ever. How did the name originate and how was it received by physicists and astronomers in the period leading up to the hot big bang consensus model in the late 1960s? How did it reflect the meanings of the origin of the universe, a concept that predates the name by nearly two decades? Contrary to what is often assumed, the name was not an instant success—it took more than twenty years before Big Bang became a household word in the scientific community. When it happened, it was used with different connotations, as is still the case. Moreover, it was used earlier and more frequently in popular than in scientific contexts, and not always relating to cosmology. It turns out that Hoyle’s celebrated name has a richer and more surprising history than commonly assumed and also that the literature on modern cosmology and its history includes many common mistakes and errors. An etymological approach centering on the name Big Bang provides supplementary insight to the historical understanding of the emergence of modern cosmology.

Quantum dynamics of the photostability of pyrazine

2015 ◽  
Vol 17 (44) ◽  
pp. 29518-29530 ◽  
Author(s):  
Matthieu Sala ◽  
Stéphane Guérin ◽  
Fabien Gatti
Keyword(s):  
Electronic State ◽  
Ground State ◽  
Quantum Dynamics ◽  
Ground Electronic State ◽  
Conical Intersection ◽  
Radiationless Decay

We propose a new mechanism for the radiationless decay of photoexcited pyrazine to its ground electronic state involving a conical intersection between the dark Au(nπ) state and the ground state.

scholarly journals Standard model and graviweak unification with (super)renormalizable gravity. Part I: Visible and invisible sectors of the universe

2015 ◽  
Vol 30 (09) ◽  
pp. 1550044 ◽  
Author(s):  
L. V. Laperashvili ◽  
H. B. Nielsen ◽  
A. Tureanu
Keyword(s):  
Standard Model ◽  
Quantum Gravity ◽  
Consistent Theory ◽  
Invariant Model ◽  
Higher Derivative ◽  
Self Consistent ◽  
Renormalizable Theory ◽  
Theory Of Gravity ◽  
Higgs Fields ◽  
The Universe

We develop a self-consistent Spin (4, 4)-invariant model of the unification of gravity with weak SU(2) gauge and Higgs fields in the visible and invisible sectors of our universe. We consider a general case of the graviweak unification, including the higher-derivative super-renormalizable theory of gravity, which is a unitary, asymptotically-free and perturbatively consistent theory of the quantum gravity.

The universe created from vacuum in the quantum-gravity interpretation of Brans-Dicke’s theory

1989 ◽  
Vol 104 (4) ◽  
pp. 467-473
Author(s):  
Liu Liao ◽  
Fan Li ◽  
Huang Chao-guang
Keyword(s):  
Quantum Gravity ◽  
Gravity Interpretation ◽  
The Universe

scholarly journals The little sibling of the big rip singularity

2015 ◽  
Vol 24 (10) ◽  
pp. 1550078 ◽  
Author(s):  
Mariam Bouhmadi-López ◽  
Ahmed Errahmani ◽  
Prado Martín-Moruno ◽  
Taoufik Ouali ◽  
Yaser Tavakoli
Keyword(s):  
Blow Up ◽  
Energy Condition ◽  
Cosmic Time ◽  
Energy Conditions ◽  
Accelerating Universe ◽  
Hubble Rate ◽  
Big Rip ◽  
The Status ◽  
The Universe ◽  
Nonlinear Energy

In this paper, we present a new cosmological event, which we named the little sibling of the big rip. This event is much smoother than the big rip singularity. When the little sibling of the big rip is reached, the Hubble rate and the scale factor blow up, but the cosmic derivative of the Hubble rate does not. This abrupt event takes place at an infinite cosmic time where the scalar curvature explodes. We show that a doomsday à la little sibling of the big rip is compatible with an accelerating universe, indeed at present it would mimic perfectly a ΛCDM scenario. It turns out that, even though the event seems to be harmless as it takes place in the infinite future, the bound structures in the universe would be unavoidably destroyed on a finite cosmic time from now. The model can be motivated by considering that the weak energy condition should not be strongly violated in our universe, and it could give us some hints about the status of recently formulated nonlinear energy conditions.

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