scholarly journals Analysis of Scalar Field Cosmology with Phase Space Deformations

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Sinuhe Perez-Payan ◽  
M. Sabido ◽  
E. Mena ◽  
C. Yee-Romero
Keyword(s):  
Phase Space ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Parameter Space ◽  
Symplectic Structure ◽  
Effective Cosmological Constant ◽  
Scalar Field Cosmology

Phase space deformations on scalar field cosmology are studied. The deformation is introduced by modifying the symplectic structure of the minisuperspace variables. The effects of the deformation are studied in the “C-frame” and the “NC-frame.” In order to remove the ambiguities of working on different frames, a new principle is introduced. When we impose that both frames should be physically equivalent, we conclude that the only possibility for this model, is to have an effective cosmological constantΛeff≥0. Finally we bound the parameter space forθandβ.

scholarly journals Quantum of the bare cosmological constant

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
Farhang Loran
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Stress Tensor ◽  
Parameter Space ◽  
Field Theories ◽  
Classical Solutions ◽  
Curved Spacetimes ◽  
Free Scalar ◽  
Scalar Theories

Abstract We show that there exist scalar field theories with plausible one-particle states in general $D$-dimensional nonstationary curved spacetimes whose propagating modes are localized on $d\le D$ dimensional hypersurfaces, and the corresponding stress tensor resembles the bare cosmological constant $\lambda_{\rm B}$ in the $D$-dimensional bulk. We show that nontrivial $d=1$ dimensional solutions correspond to $\lambda_{\rm B}< 0$. Considering free scalar theories, we find that for $d=2$ the symmetry of the parameter space of classical solutions corresponding to $\lambda_{\rm B}\neq 0$ is $O(1,1)$, which enhances to $\mathbb{Z}_2\times{\rm Diff}(\mathbb{R}^1)$ at $\lambda_{\rm B}=0$. For $d>2$ we obtain $O(d-1,1)$, $O(d-1)\times {\rm Diff}(\mathbb{R}^1)$, and $O(d-1,1)\times O(d-2)\times {\rm Diff}(\mathbb{R}^1)$ corresponding to, respectively, $\lambda_{\rm B}<0$, $\lambda_{\rm B}=0$, and $\lambda_{\rm B}>0$.

scholarly journals Dark Energy as a Cosmological Consequence of Existence of the Dirac Scalar Field in Nature

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
O. V. Babourova ◽  
B. N. Frolov
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Early Universe ◽  
Large Time ◽  
Field Equations ◽  
Conformal Theory ◽  
Effective Cosmological Constant ◽  
Theory Of Gravitation ◽  
Cosmological Consequence

The solution of the field equations of the conformal theory of gravitation with Dirac scalar field in Cartan-Weyl spacetime at the very early Universe is obtained. In this theory dark energy (described by an effective cosmological constant) is a function of the Dirac scalar field β. This solution describes the exponential decreasing of β at the inflation stage and has a limit to a constant value of the dark energy at large time. This can give a way to solving the fundamental cosmological constant problem as a consequence of the fields dynamics in the early Universe.

scholarly journals SIGNATURE CHANGE BY GUP

2013 ◽  
Vol 22 (05) ◽  
pp. 1350026 ◽  
Author(s):  
T. GHANEH ◽  
F. DARABI ◽  
H. MOTAVALLI
Keyword(s):  
Phase Space ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Generalized Uncertainty Principle ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Massive Scalar ◽  
Good Correspondence ◽  
Massive Scalar Field ◽  
Frw Metric

We revisit the issue of continuous signature transition from Euclidean to Lorentzian metrics in a cosmological model described by Friedmann–Robertson–Walker (FRW) metric minimally coupled with a self-interacting massive scalar field. Then, using a noncommutative (NC) phase space of dynamical variables deformed by generalized uncertainty principle (GUP), we show that the signature transition occurs even for a model described by the FRW metric minimally coupled with a free massless scalar field accompanied by a cosmological constant. This indicates that the continuous signature transition might have been easily occurred at early universe just by a free massless scalar field, a cosmological constant and a NC phase space deformed by GUP, without resorting to a massive scalar field having an ad hoc complicate potential. We also study the quantum cosmology of the model and obtain a solution of Wheeler–DeWitt (WD) equation which shows a good correspondence with the classical path.

scholarly journals ON THE QUASI-ISOTROPIC INFLATIONARY SOLUTION

2003 ◽  
Vol 12 (10) ◽  
pp. 1845-1857 ◽  
Author(s):  
GIOVANNI IMPONENTE ◽  
GIOVANNI MONTANI
Keyword(s):  
Scalar Field ◽  
Cosmological Constant ◽  
Small Function ◽  
Inflationary Universe ◽  
Arbitrary Form ◽  
Metric Tensor ◽  
Dominant Term ◽  
First Order ◽  
Effective Cosmological Constant ◽  
Relativistic Matter

In this paper we find a solution for a quasi-isotropic inflationary Universe which allows to introduce in the problem a certain degree of inhomogeneity. We consider a model which generalizes the (flat) FLRW one by introducing a first order inhomogeneous term, whose dynamics is induced by an effective cosmological constant. The 3-metric tensor is constituted by a dominant term, corresponding to an isotropic-like component, while the amplitude of the first order one is controlled by a "small" function η(t). In a Universe filled with ultra relativistic matter and a real self-interacting scalar field, we discuss the resulting dynamics, up to first order in η, when the scalar field performs a slow roll on a plateau of a symmetry breaking configuration and induces an effective cosmological constant. We show how the spatial distribution of the ultra relativistic matter and of the scalar field admits an arbitrary form but nevertheless, due to the required inflationary e-folding, it cannot play a serious dynamical role in tracing the process of structures formation (via the Harrison–Zeldovic spectrum). As a consequence, this paper reinforces the idea that the inflationary scenario is incompatible with a classical origin of the large scale structures.

scholarly journals Scalar field cosmology — geometry of dynamics

2014 ◽  
Vol 11 (02) ◽  
pp. 1460012 ◽  
Author(s):  
Marek Szydłowski ◽  
Orest Hrycyna ◽  
Aleksander Stachowski
Keyword(s):  
Phase Space ◽  
Scalar Field ◽  
Dynamical Systems ◽  
Potential Function ◽  
Structural Stability ◽  
Saddle Points ◽  
Scalar Fields ◽  
Fine Tuning ◽  
Scalar Field Cosmology ◽  
Structurally Stable

We study the Scalar Field Cosmology (SFC) using the geometric language of the phase space. We define and study an ensemble of dynamical systems as a Banach space with a Sobolev metric. The metric in the ensemble is used to measure a distance between different models. We point out the advantages of visualization of dynamics in the phase space. It is investigated the genericity of some class of models in the context of fine tuning of the form of the potential function in the ensemble of SFC. We also study the symmetries of dynamical systems of SFC by searching for their exact solutions. In this context, we stressed the importance of scaling solutions. It is demonstrated that scaling solutions in the phase space are represented by unstable separatrices of the saddle points. Only critical point itself located on two-dimensional stable submanifold can be identified as scaling solution. We have also found a class of potentials of the scalar fields forced by the symmetry of differential equation describing the evolution of the Universe. A class of potentials forced by scaling (homology) symmetries was given. We point out the role of the notion of a structural stability in the context of the problem of indetermination of the potential form of the SFC. We characterize also the class of potentials which reproduces the ΛCDM model, which is known to be structurally stable. We show that the structural stability issue can be effectively used is selection of the scalar field potential function. This enables us to characterize a structurally stable and therefore a generic class of SFC models. We have found a nonempty and dense subset of structurally stable models. We show that these models possess symmetry of homology.

scholarly journals SIMPLEST COSMOLOGICAL MODEL WITH THE SCALAR FIELD II.

1998 ◽  
Vol 07 (01) ◽  
pp. 129-138 ◽  
Author(s):  
A. YU. KAMENSHCHIK ◽  
I. M. KHALATNIKOV ◽  
A. V. TOPORENSKY
Keyword(s):  
Phase Space ◽  
Scalar Field ◽  
Cosmological Model ◽  
Qualitative Analysis ◽  
Cosmological Constant ◽  
Numerical Calculations ◽  
Inflaton Field ◽  
Model Combining ◽  
Friedmann Robertson Walker

Continuing the investigation of the simplest cosmological model with the massive real scalar noninteracting inflaton field minimally coupled to gravity, we study an influence of the cosmological constant on the behavior of trajectories in closed minisuperspace Friedmann–Robertson–Walker model. Combining numerical calculations with qualitative analysis both in configuration and phase space we present a convenient classification of trajectories.

scholarly journals Decrease of the effective cosmological constant in the Poincare gauge theory of gravity with a scalar field

2021 ◽  
Vol 2081 (1) ◽  
pp. 012015
Author(s):  
O V Babourova ◽  
B N Frolov
Keyword(s):  
Gauge Theory ◽  
Scalar Field ◽  
Cosmological Constant ◽  
Big Bang ◽  
Cosmological Constant Problem ◽  
Effective Cosmological Constant ◽  
Theory Of Gravity ◽  
The Big Bang ◽  
Modern Era ◽  
Gauge Theory Of Gravity

Abstract Cosmological consequences of the Poincare gauge theory of gravity are considered. An effective cosmological constant depending from the Dirac scalar field is introduced. It is proved that at the super-early Universe, the effective cosmological constant decreases exponentially from a huge value at the Big Bang to its extremely small value in the modern era, while the scale factor sharply increases and demonstrates inflationary behavior. This fact solves the well-known “cosmological constant problem” also in the Poincare gauge theory of gravity.

scholarly journals Scalar field cosmology in phase space

2012 ◽  
Vol 45 (1) ◽  
pp. 103-123 ◽  
Author(s):  
Valerio Faraoni ◽  
Charles S. Protheroe
Keyword(s):  
Phase Space ◽  
Scalar Field ◽  
Scalar Field Cosmology

scholarly journals Effects of deformed phase space on scalar field cosmology

2013 ◽  
Vol 88 (2) ◽  
Author(s):  
S. Pérez-Payán ◽  
M. Sabido ◽  
C. Yee-Romero
Keyword(s):  
Phase Space ◽  
Scalar Field ◽  
Scalar Field Cosmology
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