Cosmological scenario in κ(R,T) gravity

2021 ◽  
Author(s):  
Archana Dixit ◽  
Anirudh Pradhan ◽  
Raghavendra Chaubey
Keyword(s):  
Deceleration Parameter ◽  
Chaplygin Gas ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Eos Parameter ◽  
Dominant Component ◽  
Cosmological Scenario ◽  
Deterministic Solution ◽  
Time Periodic ◽  
The Universe

In this paper, we investigate the cosmic acceleration and the behavior of dark energy (DE) in the structure of the recently proposed [Formula: see text] gravity theory [G. R. P. Teruel, [Formula: see text] gravity, Eur. Phys. J. C 78 (2018) 660]. In this study, we obtained some fascinating cosmological features that are coherent with observational evidences and the touchstone [Formula: see text]CDM model. To find the deterministic solution, we consider a periodic deceleration parameter [Formula: see text], where [Formula: see text] [M. Shen and L. Zhao, Oscillating quintom model with time periodic varying deceleration parameter, Chin. Phys. Lett. 31 (2014) 010401], which predicts the decelerating and accelerating phases of the universe. The Equation of State (EoS) parameter also supports the idea of DE, which is the dominant component and it is responsible for the universe’s accelerated expansion. Here, we also construct cosmographic parameters, like, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and studied their evolution in spatially flat [Formula: see text] gravity. We find that these observations are sufficient in comparison with the universe’s physical and kinematic properties and also consistent with ongoing (OHD[Formula: see text][Formula: see text][Formula: see text]JLA) observation. Next, we apply the geometric diagnostics, the state-finder ([Formula: see text]) in [Formula: see text] gravity to discriminate from the [Formula: see text]CDM model. We found that our model lies in quintessence and the Chaplygin Gas region. Finally, the model approaches [Formula: see text]CDM at the present epoch of the universe.

scholarly journals Barboza–Alcaniz equation of state parametrization: Constraining the parameters in different gravity theories

2019 ◽  
Vol 34 (21) ◽  
pp. 1950163 ◽  
Author(s):  
Promila Biswas ◽  
Ritabrata Biswas
Keyword(s):  
Equation Of State ◽  
Loop Quantum Gravity ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Late Time ◽  
Eos Parameter ◽  
Whole Space ◽  
Data Points ◽  
Gravity Theories ◽  
The Universe

To justify the 20-year old distant Ia Supernova observations which revealed to us that our universe is experiencing a late-time cosmic acceleration, propositions of existence of exotic fluids inside our universe are made. These fluids are assumed to occupy homogeneously the whole space of the universe and to exert negative pressure from inside such that the late-time accelerated expansion is caused. Among the different suggested models of such exotic matters/energy popularly coined as dark matter/dark energy (DE), a well-known and popular process is “introduction of redshift parametrization” of the equation of state (EoS) parameter of these fluids. We, very particularly, take the parametrization proposed by Barboza and Alcaniz (BA) along with the cosmological constant. We use 39 data points for Hubble’s parameter calculated for different redshifts and try to constrain the DE EoS parameters for BA modeling. We then constrain the DE parametrization parameters in the background of Einstein’s general relativity, loop quantum gravity and Horava–Lifshitz gravity one after another. We find the [Formula: see text], [Formula: see text] and [Formula: see text] confidence contours for all these cases and compare them with each other. We try to speculate which gravity is constraining the parameters most and which one is letting the parameters to stay within a larger domain. We tally our results of 557 points Union2 Sample and again compare them for different gravity theories.

State finder and Om diagnostics in modified and generalised Chaplygin gas from recent data

2021 ◽  
Author(s):  
P. Thakur
Keyword(s):  
Chaplygin Gas ◽  
Red Shift ◽  
Recent Past ◽  
Eos Parameter ◽  
Deceleration Phase ◽  
Om Diagnostic ◽  
Expected Values ◽  
Best Fit ◽  
The Universe ◽  
Jerk Parameter

A modified and generalised Chaplygin gas (MCG, [Formula: see text] and GCG, [Formula: see text]) has been separately chosen here as a constituent of the universe. Concept of state finder and Om diagnostics are introduced to track the dark energy in the models. Here, observed Hubble data (OHD) and binned Pantheon data of supernovae are used to determine the best-fit equation-of-state (EoS) parameters of these models and these are compared with the [Formula: see text]CDM model. The best-fit value and expected values of cosmological jerk parameter [Formula: see text], snap parameter [Formula: see text] are determined, which are close to each other. A plot of [Formula: see text] with red-shift, with themselves, as well as with deceleration parameter [Formula: see text], shows the evolution of the universe and its possible future. Variations of [Formula: see text] and EoS parameter [Formula: see text] with red-shift show acceleration–deceleration phase transition in the recent past. Lastly, the state finder pair [Formula: see text] and Om diagnostic have been utilized to discriminate the models.

scholarly journals Dynamic of the Accelerated Expansion of the Universe in the DGP Model

2011 ◽  
Vol 21 (3) ◽  
pp. 253 ◽  
Author(s):  
Vo Quoc Phong
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Cold Dark Matter ◽  
Growth Index ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Density Parameter ◽  
Type Ia ◽  
Age Of The Universe ◽  
The Universe

According to experimental data of SNe Ia (Supernovae type Ia), we will discuss in detial dynamics of the DGP model and introduce a simple parametrization of matter $\omega$, in order to analyze scenarios of the expanding universe and the evolution of the scale factor. We find that the dimensionless matter density parameter at the present epoch $\Omega^0_m=0.3$, the age of the universe $t_0= 12.48$ Gyr, $\frac{a}{a_0}=-2.4e^{\frac{-t}{25.56}}+2.45$. The next we study the linear growth of matter perturbations, and we assume a definition of the growth rate, $f \equiv \frac{dln\delta}{dlna}$. As many authors for many years, we have been using a good approximation to the growth rate $f \approx \Omega^{\gamma(z)}_m$, we also find that the best fit of the growth index, $\gamma(z)\approx 0.687 - \frac{40.67}{1 + e^{1.7. (4.48 + z)}}$, or $\gamma(z)= 0.667 + 0.033z$ when $z\ll1$. We also compare the age of the universe and the growth index with other models and experimental data. We can see that the DGP model describes the cosmic acceleration as well as other models that usually refers to dark energy and Cold Dark Matter (CDM).

Phase space analysis of the Umami Chaplygin model

2021 ◽  
pp. 2150052
Author(s):  
Qihong Huang ◽  
Ruanjing Zhang ◽  
Jun Chen ◽  
He Huang ◽  
Feiquan Tu
Keyword(s):  
Phase Space ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Late Time ◽  
Phase Space Analysis ◽  
Space Analysis ◽  
History Of ◽  
Evolutionary Trajectories ◽  
The Universe ◽  
Universe Evolution

In this paper, we analyze the universe evolution and phase space behavior of the Umami Chaplygin model, where the Umami Chaplygin fluid replaces both a dark energy and a dark and baryonic matter. We find the Umami Chaplygin model can be stable against perturbations under some conditions and can be used to explain the late-time cosmic acceleration. The results of phase space analysis show that there exists a late-time accelerated expansion attractor with [Formula: see text], which indicates the Umami Chaplygin fluid can behave as a cosmological constant. Moreover, the Umami Chaplygin model can describe the expansion history of the universe. The evolutionary trajectories of the statefinder diagnostic pairs and the finite time future singularities are also discussed.

Pilgrim dark energy models in fractal universe

2016 ◽  
Vol 26 (06) ◽  
pp. 1750049 ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Ines G. Salako ◽  
Faiza Gulshan
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Freezing And Thawing ◽  
Eos Parameter ◽  
Pilgrim Dark Energy ◽  
Energy Models ◽  
Expansion Behavior ◽  
The Universe

We discuss the cosmological implications of interacting pilgrim dark energy (PDE) models (with Hubble, Granda–Oliveros and generalized ghost cutoffs) with cold dark matter ([Formula: see text]CDM) in fractal cosmology by assuming the flat universe. We observe that the Hubble parameter lies within observational suggested ranges while deceleration parameter represents the accelerated expansion behavior of the universe. The equation of state (EoS) parameter ([Formula: see text]) corresponds to the quintessence region and phantom region for different cases of [Formula: see text]. Further, we can see that [Formula: see text]–[Formula: see text] (where prime indicates the derivative with respect to natural logarithmic of scale factor) plane describes the freezing and thawing regions and also corresponds to [Formula: see text] limit for some cases of [Formula: see text] (PDE parameter). It is also noted that the [Formula: see text]–[Formula: see text] (state-finder parameters) plane corresponds to [Formula: see text] limit and also shows the Chaplygin as well as phantom/quintessence behavior. It is observed that pilgrim dark energy models in fractal cosmology expressed the consistent behavior with recent observational schemes.

Thermodynamics of generalized cosmic Chaplygin gas model

2016 ◽  
Vol 31 (10) ◽  
pp. 1650061 ◽  
Author(s):  
M. Sharif ◽  
Ayesha Sarwar
Keyword(s):  
Isothermal Condition ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Physical Parameters ◽  
Stability Conditions ◽  
Expansion Of The Universe ◽  
The Stability ◽  
Generalized Cosmic Chaplygin Gas ◽  
The Universe ◽  
Thermal Stability Of

In this paper, we study thermal stability of an exotic fluid known as generalized cosmic Chaplygin gas (GCCG). We evaluate different physical parameters and examine how this fluid describes accelerated expansion of the universe. The stability conditions are formulated from thermodynamics which indicate that the respective fluid is stable adiabatically but it cannot be checked under isothermal condition.

scholarly journals DARK ENERGY: A UNIFYING VIEW

2008 ◽  
Vol 17 (03n04) ◽  
pp. 651-658 ◽  
Author(s):  
WINFRIED ZIMDAHL
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Interaction Strength ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Strength Parameter ◽  
Expansion Of The Universe ◽  
Pressure Perturbations ◽  
The Universe

Different models of the cosmic substratum which pretend to describe the present stage of accelerated expansion of the Universe, like the ΛCDM model or the Chaplygin gas, can be seen as special realizations of a holographic dark energy cosmology if the option of an interaction between pressureless dark matter and dark energy is taken seriously. The corresponding interaction strength parameter plays the role of a cosmological constant. Differences occur at the perturbative level. In particular, the pressure perturbations are intrinsically nonadiabatic.

scholarly journals Accelerated expansion of the universe from the perspective of inhomogeneous cosmology

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040037
Author(s):  
Irina Bormotova ◽  
Elena Kopteva ◽  
Mariia Churilova ◽  
Zdenek Stuchlik
Keyword(s):  
Deceleration Parameter ◽  
Spherical Symmetry ◽  
Accelerated Expansion ◽  
Spatial Curvature ◽  
Inhomogeneous Cosmology ◽  
Spatial Part ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Special Case ◽  
Universe Evolution

We present a special case of the Stephani solution with spherical symmetry while considering different values of spatial curvature. We investigate the dynamics of the universe evolution in our model, build the R–T-regions for the resulting spacetime and analyze the behavior of the deceleration parameter. The singularities of the model are also discussed. The geometry of the spatial part of the obtained solution is explored.

Cosmological and thermodynamics consequences of viscous modified theories of gravity

2019 ◽  
Vol 34 (35) ◽  
pp. 1950287
Author(s):  
Abdul Jawad ◽  
Saba Qummer ◽  
Shamaila Rani ◽  
M. Younas
Keyword(s):  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Modified Theories Of Gravity ◽  
Thermal Equilibrium Condition ◽  
Entropy Variation ◽  
Expansion Of The Universe ◽  
Theories Of Gravity ◽  
Chern Simons ◽  
The Universe ◽  
Dgp Braneworld

The illustration of cosmic acceleration is being presented in the framework of DGP braneworld and dynamical Chern–Simons modified gravity in the presence of casual Israel–Stewart formalism. In this way, we discuss the evolution parameter which leads to the accelerated expansion of the universe in the phantom as well as quintessence region for both gravities. The squared speed of sound [Formula: see text] leads to the stable behavior of the current physical system in both gravities in the later epoch. Also, the entropy variation, as well as thermal equilibrium condition, remains valid in both frameworks at the present and later epoch.

Kaluza–Klein minimally interacting dark energy model in the presence of massive scalar field

2021 ◽  
Vol 36 (08) ◽  
pp. 2150054
Author(s):  
K. Dasu Naidu ◽  
Y. Aditya ◽  
R. L. Naidu ◽  
D. R. K. Reddy
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Massive Scalar ◽  
Field Equations ◽  
Eos Parameter ◽  
Massive Scalar Field ◽  
The Universe ◽  
Kaluza Klein

In this paper, our purpose is to discuss the dynamical aspects of Kaluza–Klein five-dimensional cosmological model filled with minimally interacting baryonic matter and dark energy (DE) in the presence of an attractive massive scalar field. We obtain a determinate solution of the Einstein field equations using (i) a relation between the metric potentials and (ii) a power law relation between the average scale factor of the universe and the massive scalar field. We have determined scalar field, matter energy density, DE density, equation of state (EoS) [Formula: see text], deceleration [Formula: see text] and statefinder [Formula: see text] parameters of our model. We also develop [Formula: see text]–[Formula: see text] phase, squared sound speed, statefinders and [Formula: see text]–[Formula: see text] planes in the evolving universe. It is observed that the EoS parameter exhibits quintom-like behavior from quintessence to phantom epoch by crossing the vacuum era of the universe. The squared speed of sound represents the instability of the model, whereas the [Formula: see text]–[Formula: see text] plane shows both thawing and freezing regions. The [Formula: see text]CDM limit is attained in both [Formula: see text]–[Formula: see text] and statefinder planes. We have also discussed the cosmological importance of the above parameters with reference to modern cosmology. It is found that the dynamics of these cosmological parameters indicate the accelerated expansion of the universe which is consistent with the current cosmological observations.

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