scholarly journals A Jacobian generalization of the pseudo-Nambu–Goldstone boson potential

2017 ◽  
Vol 26 (03) ◽  
pp. 1750019
Author(s):  
W. S. Hipólito-Ricaldi ◽  
J. R. Villanueva
Keyword(s):  
Equation Of State ◽  
Goldstone Boson ◽  
Data Sets ◽  
Inflationary Model ◽  
Text Data ◽  
Analytical Approximations ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Jacobian Functions ◽  
Quintessence Model

We enlarge the classes of inflaton and quintessence fields by generalizing the pseudo-Nambu–Goldstone boson potential by means of elliptic Jacobian functions, which are characterized by a parameter [Formula: see text]. We use such a generalization to implement an inflationary era and a late acceleration of the universe. As an inflationary model, the Jacobian generalization leads us to a number of e-foldings and a primordial spectrum of perturbations compatible with the Planck Collaboration 2015. As a quintessence model, a study of the evolution of its equation-of-state (EoS) and its [Formula: see text]–[Formula: see text] plane helps us to classify it as a thawing model. This allows us to consider analytical approximations for the EoS recently discovered for thawing quintessence. By using JLA supernovae Ia and Hubble parameter [Formula: see text] data sets, we perform an observational analysis of the viability of the model as quintessence.

scholarly journals Chameleon field dynamics during inflation

2018 ◽  
Vol 27 (04) ◽  
pp. 1850041 ◽  
Author(s):  
Nasim Saba ◽  
Mehrdad Farhoudi
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
State Parameter ◽  
Big Bang ◽  
Late Time ◽  
Inflationary Model ◽  
Slow Roll ◽  
Equation Of State Parameter ◽  
The Common ◽  
The Universe

By studying the chameleon model during inflation, we investigate whether it can be a successful inflationary model, wherein we employ the common typical potential usually used in the literature. Thus, in the context of the slow-roll approximations, we obtain the e-folding number for the model to verify the ability of resolving the problems of standard big bang cosmology. Meanwhile, we apply the constraints on the form of the chosen potential and also on the equation of state parameter coupled to the scalar field. However, the results of the present analysis show that there is not much chance of having the chameleonic inflation. Hence, we suggest that if through some mechanism the chameleon model can be reduced to the standard inflationary model, then it may cover the whole era of the universe from the inflation up to the late time.

scholarly journals DIRECT DETERMINATIONS OF THE REDSHIFT BEHAVIOR OF THE PRESSURE, ENERGY DENSITY, AND EQUATION OF STATE OF THE DARK ENERGY AND THE ACCELERATION OF THE UNIVERSE

2005 ◽  
Vol 20 (06) ◽  
pp. 1113-1120 ◽  
Author(s):  
RUTH A. DALY ◽  
S. G. DJORGOVSKI
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Radio Galaxy ◽  
A Priori ◽  
Acceleration Rate ◽  
Acceleration Of The Universe ◽  
Theory Of Gravity ◽  
The Universe

One of the goals of current cosmological studies is the determination of the expansion and acceleration rates of the universe as functions of redshift, and the determination of the properties of the dark energy that can explain these observations. Here the expansion and acceleration rates are determined directly from the data, without the need for the specification of a theory of gravity, and without adopting an a priori parameterization of the form or redshift evolution of the dark energy. We use the latest set of distances to SN standard candles from Riess et al. (2004), supplemented by data on radio galaxy standard ruler sizes, as described by Daly & Djorgovski (2003, 2004). We find that the universe transitions from acceleration to deceleration at a redshift of zT≈0.4, with the present value of q0=-0.35±0.15. The standard "concordance model" with Ω0=0.3 and Λ=0.7 provides a reasonably good fit to the dimensionless expansion rate as a function of redshift, though it fits the dimensionless acceleration rate as a function of redshift less well. The expansion and acceleration rates are then combined with a theory of gravity to determine the pressure, energy density, and equation of state of the dark energy as functions of redshift. Adopting General Relativity as the correct theory of gravity, the redshift trends for the pressure, energy density, and equation of state of the dark energy out to z~1 are determined, and are found to be generally consistent with the concordance model; they have zero redshift values of p0=-0.6±0.15, f0=0.62±0.05, and w0=-0.9±0.1.

scholarly journals SNe Ia as a cosmological probe

2015 ◽  
Vol 24 (14) ◽  
pp. 1530029 ◽  
Author(s):  
Xiangcun Meng ◽  
Yan Gao ◽  
Zhanwen Han
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
High Redshift ◽  
Type Ia Supernovae ◽  
Analysis Techniques ◽  
Type Ia ◽  
History Of ◽  
Acceleration Of The Universe ◽  
Ia Supernovae ◽  
The Universe

Type Ia supernovae (SNe Ia) luminosities can be corrected in order to render them useful as standard candles that are able to probe the expansion history of the universe. This technique was successfully applied to discover the present acceleration of the universe. As the number of SNe Ia observed at high redshift increases and analysis techniques are perfected, people aim to use this technique to probe the equation-of-state of the dark energy (EOSDE). Nevertheless, the nature of SNe Ia progenitors remains controversial and concerns persist about possible evolution effects that may be larger and harder to characterize than the more obvious statistical uncertainties.

scholarly journals The Lambert W Function: A Newcomer in the Cosmology Class?

2019 ◽  
Vol 75 (1) ◽  
pp. 23-27
Author(s):  
Subhajit Saha ◽  
Kazuharu Bamba
Keyword(s):  
Equation Of State ◽  
Evolutionary History ◽  
Initial Singularity ◽  
Lambert W Function ◽  
Late Time ◽  
Unknown Parameters ◽  
Late Time Acceleration ◽  
History Of ◽  
Acceleration Of The Universe ◽  
The Universe

AbstractWe propose a novel equation of state (EoS) which explains the evolutionary history of a flat Friedmann–Lemaitre–Robertson–Walker universe. The uniqueness of this EoS lies in the fact that it incorporates the Lambert W function in a special fashion. It is explicitly demonstrated that with observationally relevant values of the unknown parameters ϑ1 and ϑ2, all the evolutionary phases of the universe can be reproduced. Moreover, it also shows that the initial singularity is unavoidable and asserts that the late-time acceleration of the universe would continue forever.

scholarly journals Invisible QCD as Dark Energy

Universe ◽  
2020 ◽  
Vol 6 (6) ◽  
pp. 75
Author(s):  
Andrea Addazi ◽  
Stephon Alexander ◽  
Antonino Marcianò
Keyword(s):  
Dark Energy ◽  
Stability Analysis ◽  
Equation Of State ◽  
Quantum Chromodynamics ◽  
Early Universe ◽  
Negative Pressure ◽  
Late Time ◽  
Late Time Acceleration ◽  
Acceleration Of The Universe ◽  
The Universe

We account for the late time acceleration of the Universe by extending the Quantum Chromodynamics (QCD) color to a S U ( 3 ) invisible sector (IQCD). If the Invisible Chiral symmetry is broken in the early universe, a condensate of dark pions (dpions) and dark gluons (dgluons) forms. The condensate naturally forms due to strong dynamics similar to the Nambu–Jona-Lasinio mechanism. As the Universe evolves from early times to present times the interaction energy between the dgluon and dpion condensate dominates with a negative pressure equation of state and causes late time acceleration. We conclude with a stability analysis of the coupled perturbations of the dark pions and dark gluons.

scholarly journals SCALAR NONLUMINOUS MATTER IN GALAXIES

2002 ◽  
Vol 17 (04) ◽  
pp. 555-560 ◽  
Author(s):  
BYUNG JOO LEE ◽  
TAE HOON LEE
Keyword(s):  
Rotational Velocity ◽  
Scalar Potential ◽  
Scalar Fields ◽  
Global Symmetry ◽  
Late Time ◽  
Complex Scalar ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Static Space ◽  
Quintessence Model

As a candidate for dark matter in galaxies, we study an SU(3) triplet of complex scalar fields which are nonminimally coupled to gravity. In the spherically symmetric static space–time where the flat rotational velocity curves of stars in galaxies can be explained, we find simple solutions of scalar fields with SU(3) global symmetry broken to U(1) × U(1), in an exponential scalar potential, which will be useful in a quintessence model of the late-time acceleration of the universe.

IS MODIFIED CHAPLYGIN GAS ALONG WITH BAROTROPIC FLUID RESPONSIBLE FOR ACCELERATION OF THE UNIVERSE?

2007 ◽  
Vol 22 (24) ◽  
pp. 1805-1812 ◽  
Author(s):  
WRITAMBHARA CHAKRABORTY ◽  
UJJAL DEBNATH
Keyword(s):  
Chaplygin Gas ◽  
Fluid Models ◽  
Modified Chaplygin Gas ◽  
Statefinder Parameters ◽  
Barotropic Fluid ◽  
Barotropic Equation ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Two Fluid ◽  
Quintessence Model

In this letter, we consider a model of the universe filled with modified Chaplygin gas and another fluid (with barotropic equation of state) and its role in accelerating phase of the universe. We have assumed that the mixture of these two fluid models is valid from (i) the radiation era to ΛCDM for -1 ≤ γ ≤ 1 and (ii) the radiation era to quintessence model for γ < -1. For these two fluid models, the statefinder parameters describe different phase of the evolution of the universe.

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