scholarly journals Quantum Cosmologies Under Geometrical Unification of Gravity and Dark Energy

Symmetry ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 860 ◽  
Author(s):  
Carlos A. Rubio ◽  
Felipe A. Asenjo ◽  
Sergio A. Hojman
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Field Potential ◽  
Constraint Equation ◽  
Spinless Particle ◽  
Quantization Scheme ◽  
Dynamical Equations ◽  
Order Constraint ◽  
The Universe ◽  
Friedmann Robertson Walker

A Friedmann–Robertson–Walker Universe was studied with a dark energy component represented by a quintessence field. The Lagrangian for this system, hereafter called the Friedmann–Robertson–Walker–quintessence (FRWq) system, was presented. It was shown that the classical Lagrangian reproduces the usual two (second order) dynamical equations for the radius of the Universe and for the quintessence scalar field, as well as a (first order) constraint equation. Our approach naturally unified gravity and dark energy, as it was obtained that the Lagrangian and the equations of motion are those of a relativistic particle moving on a two-dimensional, conformally flat spacetime. The conformal metric factor was related to the dark energy scalar field potential. We proceeded to quantize the system in three different schemes. First, we assumed the Universe was a spinless particle (as it is common in literature), obtaining a quantum theory for a Universe described by the Klein–Gordon equation. Second, we pushed the quantization scheme further, assuming the Universe as a Dirac particle, and therefore constructing its corresponding Dirac and Majorana theories. With the different theories, we calculated the expected values for the scale factor of the Universe. They depend on the type of quantization scheme used. The differences between the Dirac and Majorana schemes are highlighted here. The implications of the different quantization procedures are discussed. Finally, the possible consequences for a multiverse theory of the Dirac and Majorana quantized Universe are briefly considered.

The BICEP2 data and a single Higgs-like interacting scalar field

2014 ◽  
Vol 23 (09) ◽  
pp. 1450075 ◽  
Author(s):  
Murli Manohar Verma ◽  
Shankar Dayal Pathak
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Gravity Waves ◽  
Field Potential ◽  
Thermodynamical Equilibrium ◽  
Conservation Of Energy ◽  
Order Of Magnitude ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Perturbed Equation

It is proposed that the recently announced BICEP2 value of tensor-to-scalar ratio r ~ 0.2 can be explained as containing an extra contribution from the recent acceleration of the universe. In fact this contribution, being robust, recent and of much longer duration (by a large order of magnitude) may dominate the contribution from the inflationary origin. In a possible scenario, matter (dark or baryonic) and radiation etc. can emerge from a single Higgs-like tachyonic scalar field in the universe through a physical mechanism not yet fully known to us. The components interact among themselves to achieve the thermodynamical equilibrium in the evolution of the universe. The field potential for the present acceleration of the universe would give a boost to the amplitude of the tensor fluctuations of gravity waves generated by the early inflation and the net effects may be higher than the earlier Planck bounds. In the process, the dark energy, as a cosmological constant decays into creation of dark matter. The diagnostics for the three-component, spatially homogeneous tachyonic scalar field are discussed in detail. The components of the field with perturbed equation of state (EoS) are taken to interact mutually and the conservation of energy for individual components gets violated. We study mainly the Om(x) diagnostics with the observed set of H(z) values at various redshifts, and the dimensionless statefinders for these interacting components. This analysis provides a strong case for the interacting dark energy in our model.

Tsallis holographic dark energy models in axially symmetric space time

2020 ◽  
Vol 17 (01) ◽  
pp. 2050011 ◽  
Author(s):  
Vipin Chandra Dubey ◽  
Ambuj Kumar Mishra ◽  
Shikha Srivastava ◽  
Umesh Kumar Sharma
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Holographic Dark Energy ◽  
Field Potential ◽  
Accelerated Expansion ◽  
Anisotropic Universe ◽  
Axially Symmetric ◽  
Eos Parameter ◽  
Quintessence Field ◽  
The Universe

In this work, we have examined the behavior of Bianchi-I (axially symmetric) matter-dominated and the anisotropic Universe with the proposed dark energy, Tsallis holographic dark energy (THDE), with the Hubble horizon as infrared cut-off [Tavayef et al., Tsallis holographic dark energy, Phys. Lett. B 781 (2018) 195–200]. The Universe evolution from matter-dominated epoch to dark energy dominated epoch is described by our proposed THDE model. The EoS parameter in our THDE model explains the evolution of the Universe according to the value of nonextensive or Tsallis parameter [Formula: see text], phantom era ([Formula: see text]) or quintom (phantom line crossing) and the quintessence era ([Formula: see text]), before reaching to completely dark energy-dominated era in the future. Additionally, we also plan to reconcile the dark energy by the method of reconstructing the evolution of the scalar field potential. For the analysis, we take into account the quintessence field and phantom scalar field for this reconstruction, which at present shows the accelerated expansion.

scholarly journals Ghost Chaplygin scalar field model of dark energy

2013 ◽  
Vol 91 (1) ◽  
pp. 54-59 ◽  
Author(s):  
F. Adabi ◽  
K. Karami ◽  
M. Mousivand
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Field Model ◽  
Accelerated Expansion ◽  
Scalar Field Model ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Friedmann Robertson Walker

We investigate the correspondence between the ghost and Chaplygin scalar field dark energy models in the framework of Einstein gravity. We consider a spatially nonflat Friedmann–Robertson–Walker universe containing dark energy that interacts with dark matter. We reconstruct the potential and the dynamics for the Chaplygin scalar field model according to the evolutionary behavior of ghost dark energy, which can describe the phantomic accelerated expansion of the universe.

scholarly journals Isotropic exact solutions in $$F(R,Y,\phi )$$ gravity via Noether symmetries

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Saira Waheed ◽  
Iqra Nawazish ◽  
M. Zubair
Keyword(s):  
Scalar Field ◽  
Exact Solutions ◽  
Field Potential ◽  
Noether Symmetries ◽  
Dynamical Equations ◽  
Curvature Invariant ◽  
Gauge Symmetries ◽  
Cosmic Evolution ◽  
Fluid Matter ◽  
Alpha Beta

AbstractThe present article investigates the existence of Noether and Noether gauge symmetries of flat Friedman–Robertson–Walker universe model with perfect fluid matter ingredients in a generalized scalar field formulation namely $$f(R,Y,\phi )$$ f ( R , Y , ϕ ) gravity, where R is the Ricci scalar and Y denotes the curvature invariant term defined by $$Y=R_{\alpha \beta }R^{\alpha \beta }$$ Y = R α β R α β , while $$\phi $$ ϕ represents scalar field. For this purpose, we assume different general cases of generic $$f(R,Y,\phi )$$ f ( R , Y , ϕ ) function and explore its possible forms along with field potential $$V(\phi )$$ V ( ϕ ) by taking constant and variable coupling function of scalar field $$\omega (\phi )$$ ω ( ϕ ) . In each case, we find non-trivial symmetry generator and its related first integrals of motion (conserved quantities). It is seen that due to complexity of the resulting system of Lagrange dynamical equations, it is difficult to find exact cosmological solutions except for few simple cases. It is found that in each case, the existence of Noether symmetries leads to power law form of scalar field potential and different new types of generic function. For the acquired exact solutions, we discuss the cosmology generated by these solutions graphically and discuss their physical significance which favors the accelerated expanding eras of cosmic evolution.

scholarly journals The cosmological behavior and the statefinder diagnosis for the New Tsallis agegraphic dark energy

2020 ◽  
Vol 35 (38) ◽  
pp. 2050318
Author(s):  
Umesh Kumar Sharma ◽  
Shikha Srivastava
Keyword(s):  
Dark Energy ◽  
Dynamical Analysis ◽  
Current Phase ◽  
Statefinder Parameters ◽  
Frw Universe ◽  
Eos Parameter ◽  
Agegraphic Dark Energy ◽  
Evolutionary Trajectories ◽  
The Universe ◽  
Friedmann Robertson Walker

In this work, we have considered the recently proposed new Tsallis agegraphic dark energy (NTADE) model [Mod. Phys. Lett. A 34, 1950086 (2019)] within the framework of a flat Friedmann–Robertson–Walker (FRW) Universe by taking various values of the parameter [Formula: see text]. The NTADE model shows the current phase transition of the Universe from decelerated to accelerated phase. The NTADE equation of state (EoS) parameter shows a rich behavior as it can be quintessence-like or phantom-like depending on the value of [Formula: see text]. For discriminating the NTADE model from [Formula: see text]CDM, we have plotted the statefinder parameters [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text] pair. The NTADE model shows distinct evolutionary trajectories of their evolution in ([Formula: see text]) and ([Formula: see text]) plane. An analysis using the snap parameter and the [Formula: see text] pair dynamical analysis have also been performed.

Evolution of the Universe with two rotating fluids

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040042
Author(s):  
V. F. Panov ◽  
O. V. Sandakova ◽  
E. V. Kuvshinova ◽  
D. M. Yanishevsky
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Scalar Field ◽  
Bianchi Type ◽  
Relativity Theory ◽  
Anisotropic Fluid ◽  
Rotating Fluids ◽  
General Relativity Theory ◽  
Exponential Expansion ◽  
The Universe

An anisotropic cosmological model with expansion and rotation and the Bianchi type IX metric has been constructed within the framework of general relativity theory. The first inflation stage of the Universe filled with a scalar field and an anisotropic fluid is considered. The model describes the Friedman stage of cosmological evolution with subsequent transition to accelerated exponential expansion observed in the present epoch. The model has two rotating fluids: the anisotropic fluid and dust-like fluid. In the approach realized in the model, the anisotropic fluid describes the rotating dark energy.

scholarly journals CAN BRANS–DICKE SCALAR FIELD ACCOUNT FOR DARK ENERGY AND DARK MATTER?

2006 ◽  
Vol 21 (15) ◽  
pp. 1241-1248 ◽  
Author(s):  
M. ARIK ◽  
M. C. ÇALIK
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Energy Density ◽  
Late Time ◽  
Energy Contribution ◽  
Time Solution ◽  
The Universe

By using a linearized non-vacuum late time solution in Brans–Dicke cosmology, we account for the 75% dark energy contribution but not for approximately 23% dark matter contribution to the present day energy density of the universe.

scholarly journals CONSTRAINING TEVES GRAVITY AS EFFECTIVE DARK MATTER AND DARK ENERGY

2007 ◽  
Vol 16 (12a) ◽  
pp. 2055-2063 ◽  
Author(s):  
HONGSHENG ZHAO
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Dual Roles ◽  
Acceleration Of The Universe ◽  
The Universe

The phenomena customarily described with the standard ΛCDM model are broadly reproduced by an extremely simple model in TeVeS, Bekenstein's1 modification of general relativity motivated by galaxy phenomenology. Our model can account for the acceleration of the Universe seen at SNeIa distances without a cosmological constant, and the accelerations seen in rotation curves of nearby spiral galaxies and gravitational lensing of high-redshift elliptical galaxies without cold dark matter. The model is consistent with BBN and the neutrino mass between 0.05 eV to 2 eV. The TeVeS scalar field is shown to play the effective dual roles of dark matter and dark energy, with the amplitudes of the effects controlled by a μ function of the scalar field, called the μ essence here. We also discuss outliers to the theory's predictions on multiimaged galaxy lenses and outliers on the subgalaxy scale.

THE ROLE OF A CHAMELEON FIELD IN AN ANISOTROPIC UNIVERSE WITH LOGAMEDIATE AND INTERMEDIATE SCENARIOS

2010 ◽  
Vol 25 (24) ◽  
pp. 4691-4701 ◽  
Author(s):  
SHUVENDU CHAKRABORTY ◽  
UJJAL DEBNATH
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Anisotropic Universe ◽  
Anisotropic Model ◽  
Scale Factors ◽  
Slow Roll ◽  
Energy Scalar ◽  
The Universe

In this work, we consider the Universe is being filled with matter composed of a chameleon-type dark energy scalar field. Employing a particular form of potential, we discuss the field's role in the accelerating phase of the Universe for an anisotropic model using the logamediate and intermediate forms of scale factors. The natures of statefinder and slow-roll parameters are discussed diagrammatically.

scholarly journals ON THE DYNAMICS OF A QUADRATIC SCALAR FIELD POTENTIAL

2009 ◽  
Vol 18 (04) ◽  
pp. 621-634 ◽  
Author(s):  
L. ARTURO UREÑA-LÓPEZ ◽  
MAYRA J. REYES-IBARRA
Keyword(s):  
Scalar Field ◽  
Autonomous System ◽  
Equations Of Motion ◽  
Scalar Potential ◽  
Field Potential ◽  
System Of Equations ◽  
New Formalism ◽  
Slow Roll ◽  
Chaotic Model ◽  
Friedmann Robertson Walker

We review the attractor properties of the simplest chaotic model of inflation, in which a minimally coupled scalar field is endowed with a quadratic scalar potential. The equations of motion in a flat Friedmann–Robertson–Walker universe are written as an autonomous system of equations, and the solutions of physical interest appear as critical points. This new formalism is then applied to the study of inflation dynamics, in which we can go beyond the known slow-roll approximation.

Sign in / Sign up

Export Citation Format

Share Document