scholarly journals Bouncing Quantum Cosmology

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 110
Author(s):  
Nelson Pinto-Neto
Keyword(s):  
Dark Matter ◽  
Quantum Theory ◽  
Dark Energy ◽  
Quantum Cosmology ◽  
Canonical Quantization ◽  
Quantization Scheme ◽  
Physical Effects ◽  
Planck Energy ◽  
De Broglie Bohm

The goal of this contribution is to present the properties of a class of quantum bouncing models in which the quantum bounce originates from the Dirac canonical quantization of a midi-superspace model composed of a homogeneous and isotropic background, together with small inhomogeneous perturbations. The resulting Wheeler-DeWitt equation is interpreted in the framework of the de Broglie-Bohm quantum theory, enormously simplifying the calculations, conceptually and technically. It is shown that the resulting models are stable and they never get to close to the Planck energy, where another more involved quantization scheme would have to be evoked, and they are compatible with present observations. Some physical effects around the bounce are discussed, like baryogenesis and magnetogenesis, and the crucial role of dark matter and dark energy is also studied.

The Nexus graviton: A quantum of Dark Energy and Dark Matter

2014 ◽  
Vol 11 (06) ◽  
pp. 1450059 ◽  
Author(s):  
Stuart Marongwe
Keyword(s):  
Dark Matter ◽  
Quantum Theory ◽  
Dark Energy ◽  
Space Time ◽  
Current Paper ◽  
Quantum Vacuum ◽  
Self Consistent ◽  
Published Paper

In a recently published paper called Nexus: A quantum theory of space-time, gravity and the quantum vacuum by the above author, a plausible self-consistent quantum theory of space-time, gravity and the quantum vacuum is provided. In this current paper the author focuses primarily on the graviton as described in Nexus as a solution to the enigmatic phenomena of Dark Energy and Dark Matter as well as includes corrections to the first paper.

scholarly journals The de Broglie–Bohm Quantum Theory and Its Application to Quantum Cosmology

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 134
Author(s):  
Nelson Pinto-Neto
Keyword(s):  
Quantum Theory ◽  
Configuration Space ◽  
Physical System ◽  
Quantum Cosmology ◽  
Dynamical Theory ◽  
Cosmological Models ◽  
Cosmological Perturbations ◽  
Alternative Description ◽  
Quantum Phenomena ◽  
De Broglie Bohm

We review the de Broglie–Bohm quantum theory. It is an alternative description of quantum phenomena in accordance with all the quantum experiments already performed. Essentially, it is a dynamical theory about objectively real trajectories in the configuration space of the physical system under investigation. Hence, it is not necessarily probabilistic, and it dispenses with the collapse postulate, making it suitable to be applied to cosmology. The emerging cosmological models are usually free of singularities, with a bounce connecting a contracting era with an expanding phase, which we are now observing. A theory of cosmological perturbations can also be constructed under this framework, which can be successfully confronted with current observations, and can complement inflation or even be an alternative to it.

scholarly journals ON THE WIDTH OF THE LAST SCATTERING SURFACE

2004 ◽  
Vol 13 (07) ◽  
pp. 1425-1429
Author(s):  
NILZA PIRES ◽  
MARIA ASSUNTA S. NOBRE ◽  
JOSÉ A. S. LIMA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Chaplygin Gas ◽  
Microwave Background ◽  
Energy Plus ◽  
Microwave Background Radiation ◽  
Physical Effects ◽  
Weakly Dependent

We discuss the physical effects of some accelerated world models on the width of the last scattering surface (LSS) of the cosmic microwave background radiation (CMBR). The models considered in our analysis are X-matter (XCDM) and a Chaplygin type gas. The redshift of the LSS does not depend on the kind of dark energy (if XCDM of Chaplygin). Further, for a Chaplygin gas, the width of the LSS is also only weakly dependent on the kind of scenario (if we have dark energy plus cold dark matter or the unified picture).

scholarly journals HOLOGRAPHIC INTERACTING DARK ENERGY IN THE BRANEWORLD COSMOLOGY

2007 ◽  
Vol 22 (35) ◽  
pp. 2631-2645 ◽  
Author(s):  
KYOUNG YEE KIM ◽  
HYUNG WON LEE ◽  
YUN SOO MYUNG
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Equations Of State ◽  
Brane Cosmology ◽  
General Decay Rate ◽  
Braneworld Cosmology ◽  
State Formula ◽  
Unified Description

We investigate a model of brane cosmology to find a unified description of the radiation-matter-dark energy universe. It is of the interacting holographic dark energy with a bulk-holographic matter χ. This is a five-dimensional cold dark matter, which plays a role of radiation on the brane. Using the effective equations of state [Formula: see text] instead of the native equations of state ωΛ, we show that this model cannot accommodate any transition from the dark energy with [Formula: see text] to the phantom regime [Formula: see text]. Furthermore, the case of interaction between four-dimensional cold dark matter and five-dimensional cold dark matter is considered for completeness. Here we find that the redshift of matter-radiation equality z eq is the same order as [Formula: see text]. Finally, we obtain a general decay rate Γ which is suitable for describing all interactions.

scholarly journals Unifying dark matter and dark energy with non-canonical scalars

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Swagat S. Mishra ◽  
Varun Sahni
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
General Condition ◽  
Cold Dark Matter ◽  
Scalar Fields ◽  
Kinetic Term ◽  
Potential Term ◽  
Small Scales ◽  
Type Potential

AbstractNon-canonical scalar fields with the Lagrangian $${{\mathcal {L}}} = X^\alpha - V(\phi )$$ L = X α - V ( ϕ ) , possess the attractive property that the speed of sound, $$c_s^{2} = (2\,\alpha - 1)^{-1}$$ c s 2 = ( 2 α - 1 ) - 1 , can be exceedingly small for large values of $$\alpha $$ α . This allows a non-canonical field to cluster and behave like warm/cold dark matter on small scales. We derive a general condition on the potential in order to facilitate the kinetic term $$X^\alpha $$ X α to play the role of dark matter, while the potential term $$V(\phi )$$ V ( ϕ ) playing the role of dark energy at late times. We demonstrate that simple potentials including $$V= V_0\coth ^2{\phi }$$ V = V 0 coth 2 ϕ and a Starobinsky-type potential can unify dark matter and dark energy. Cascading dark energy, in which the potential cascades to lower values in a series of discrete steps, can also work as a unified model.

The Role of Dark Matter and Dark Energy in Cosmological Models: Theoretical Overview

2009 ◽  
pp. 353-365
Author(s):  
A. F. Zakharov ◽  
S. Capozziello ◽  
F. De Paolis ◽  
G. Ingrosso ◽  
A. A. Nucita
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Models ◽  
Theoretical Overview

scholarly journals PSEUDO-HERMITIAN REPRESENTATION OF QUANTUM MECHANICS

2010 ◽  
Vol 07 (07) ◽  
pp. 1191-1306 ◽  
Author(s):  
ALI MOSTAFAZADEH
Keyword(s):  
Hilbert Space ◽  
Quantum Mechanics ◽  
Quantum Chaos ◽  
Relativistic Quantum ◽  
Canonical Quantization ◽  
Inner Product ◽  
Relativistic Quantum Mechanics ◽  
Real Spectrum ◽  
Quantization Scheme

A diagonalizable non-Hermitian Hamiltonian having a real spectrum may be used to define a unitary quantum system, if one modifies the inner product of the Hilbert space properly. We give a comprehensive and essentially self-contained review of the basic ideas and techniques responsible for the recent developments in this subject. We provide a critical assessment of the role of the geometry of the Hilbert space in conventional quantum mechanics to reveal the basic physical principle motivating our study. We then offer a survey of the necessary mathematical tools, present their utility in establishing a lucid and precise formulation of a unitary quantum theory based on a non-Hermitian Hamiltonian, and elaborate on a number of relevant issues of fundamental importance. In particular, we discuss the role of the antilinear symmetries such as [Formula: see text], the true meaning and significance of the so-called charge operators [Formula: see text] and the [Formula: see text]-inner products, the nature of the physical observables, the equivalent description of such models using ordinary Hermitian quantum mechanics, the pertaining duality between local-non-Hermitian versus nonlocal-Hermitian descriptions of their dynamics, the corresponding classical systems, the pseudo-Hermitian canonical quantization scheme, various methods of calculating the (pseudo-) metric operators, subtleties of dealing with time-dependent quasi-Hermitian Hamiltonians and the path-integral formulation of the theory, and the structure of the state space and its ramifications for the quantum Brachistochrone problem. We also explore some concrete physical applications and manifestations of the abstract concepts and tools that have been developed in the course of this investigation. These include applications in nuclear physics, condensed matter physics, relativistic quantum mechanics and quantum field theory, quantum cosmology, electromagnetic wave propagation, open quantum systems, magnetohydrodynamics, quantum chaos and biophysics.

scholarly journals QUANTUM THEORY OF AN ACCELERATING UNIVERSE

2008 ◽  
Vol 17 (08) ◽  
pp. 1213-1228 ◽  
Author(s):  
PEDRO F. GONZÁLEZ-DÍAZ ◽  
SALVADOR ROBLES-PÉREZ
Keyword(s):  
Information Theory ◽  
Wave Function ◽  
Quantum Theory ◽  
Dark Energy ◽  
Quantum Information ◽  
Density Matrix ◽  
Quantum Cosmology ◽  
Quantum Information Theory ◽  
Accelerating Universe ◽  
Big Rip

We review some of the well-known features of quantum cosmology, such as the factor ordering problem, the wave function and the density matrix, for a dark-energy-dominated universe, where analytical solutions can be obtained. For the particular case of the phantom universe, we suggest a quantum system in which the usual notion of locality (nonlocality) of quantum information theory has to be extended. In that case, we deal also with a quantum description where the existence of a nonchronal region around the big rip singularity is explicitly accounted for.

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