scholarly journals Constraining effective equation of state in f(Q, T) gravity

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Simran Arora ◽  
Abhishek Parida ◽  
P. K. Sahoo
Keyword(s):  
Equation Of State ◽  
State Parameter ◽  
Momentum Tensor ◽  
Accelerated Expansion ◽  
Dark Sector ◽  
Effective Equation ◽  
Best Fitting ◽  
Expansion Of The Universe ◽  
Two Parameters ◽  
The Universe

AbstractNew high-precision observations are now possible to constrain different gravity theories. To examine the accelerated expansion of the Universe, we used the newly proposed f(Q, T) gravity, where Q is the non-metricity, and T is the trace of the energy–momentum tensor. The investigation is carried out using a parameterized effective equation of state with two parameters, m and n. We have also considered the linear form of $$f(Q,T)= Q+bT$$ f ( Q , T ) = Q + b T , where b is constant. By constraining the model with the recently published 1048 Pantheon sample, we were able to find the best fitting values for the parameters b, m, and n. The model appears to be in good agreement with the observations. Finally, we analyzed the behavior of the deceleration parameter and equation of state parameter. The results support the feasibility of f(Q, T) as a promising theory of gravity, illuminating a new direction towards explaining the Universe dark sector.

ENTROPY CORRECTED HOLOGRAPHIC DARK ENERGY f(T) GRAVITY MODEL

2014 ◽  
Vol 29 (02) ◽  
pp. 1450015 ◽  
Author(s):  
M. SHARIF ◽  
SHAMAILA RANI
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Phase Plane ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Statefinder Parameters ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Evolution Trajectory

This paper is devoted to study the power-law entropy corrected holographic dark energy (ECHDE) model in the framework of f(T) gravity. We assume infrared (IR) cutoff in terms of Granda–Oliveros (GO) length and discuss the constructed f(T) model in interacting as well as in non-interacting scenarios. We explore some cosmological parameters like equation of state (EoS), deceleration, statefinder parameters as well as ωT–ωT′ analysis. The EoS and deceleration parameters indicate phantom behavior of the accelerated expansion of the universe. It is mentioned here that statefinder trajectories represent consistent results with ΛCDM limit, while evolution trajectory of ωT–ωT′ phase plane does not approach to ΛCDM limit for both interacting and non-interacting cases.

scholarly journals On a Slightly Different Power Law-Scaling for the Flat Universe

2020 ◽  
Vol 12 (4) ◽  
pp. 569-574
Author(s):  
C. Sivakumar ◽  
R. Francis
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Power Law ◽  
Hubble Parameter ◽  
State Parameter ◽  
Effective Equation ◽  
Flat Universe ◽  
Equation Of State Parameter ◽  
Age Of The Universe ◽  
The Universe

A slightly different power law-scaling fits to the picture of our 13.7 billion years old flat universe which is expanding presently at 67 km/s/Mpc with an acceleration. The model which is an attempt to retain power-law scaling in the light of the accepted facts about the universe we are living in, has a constant effective equation of state parameter as the cosmic fluid is a solution of matter, radiation and dark energy. It is successful in explaining the acceleration of universe which the normal power law fails if the present Hubble parameter is 67 km/s/Mpc and age of the universe is 13.7 billion years, and it is free from the defect of singularity.

scholarly journals Dynamical Properties of Dark Energy Models in Fractal Universe

Symmetry ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1174
Author(s):  
Muhammad Umair Shahzad ◽  
Ayesha Iqbal ◽  
Abdul Jawad
Keyword(s):  
Dark Energy ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Accelerating Universe ◽  
Statefinder Parameters ◽  
Om Diagnostic ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
Dynamical Properties ◽  
The Universe

In this paper, we consider the flat FRW spacetime filled with interacting dark energy and dark matter in fractal universe. We work with the three models of dark energy named as Tsallis, Renyi and Sharma–Mittal. We investigate different cosmological implications such as equation of state parameter, squared speed of sound, deceleration parameter, statefinder parameters, ω e f f - ω e f f ´ (where prime indicates the derivative with respect to ln a , and a is cosmic scale factor) plane and Om diagnostic. We explore these parameters graphically to study the evolving universe. We compare the consistency of dark energy models with the accelerating universe observational data. All three models are stable in fractal universe and support accelerated expansion of the universe.

THREE COMPONENTS EVOLUTION IN A SIMPLE BIG BOUNCE COSMOLOGICAL MODEL

2005 ◽  
Vol 14 (05) ◽  
pp. 883-891 ◽  
Author(s):  
LIXIN XU ◽  
HONGYA LIU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Model ◽  
Accelerated Expansion ◽  
Ricci Flat ◽  
Bouncing Cosmology ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Three Components ◽  
Big Bounce

We consider a five-dimensional Ricci flat Bouncing cosmology and assume that the four-dimensional universe is permeated smoothly by three minimally coupled matter components: CDM + baryons ρm, radiation ρr and dark energy ρx. Evolutions of these three components are studied and it is found that dark energy dominates before the bounce, and pulls the universe contracting. In this process, dark energy decreases while radiation and the matter increases. After the bounce, the radiation and matter dominates alternatively and then decreases with the expansion of the universe. At present, the dark energy dominates again and pushes the universe accelerating. In this model, we also obtain that the equation of state (EOS) of dark energy at present time is wx0≈-1.05 and the redshift of the transition from decelerated expansion to accelerated expansion is zT≈0.37, which are compatible with the current observations.

scholarly journals Accelerated expansion of the Universe in the presence of dark matter pressure

2020 ◽  
Vol 98 (2) ◽  
pp. 210-216
Author(s):  
Zeinab Rezaei
Keyword(s):  
Dark Matter ◽  
Equation Of State ◽  
Hubble Parameter ◽  
Energy Equation ◽  
Accelerated Expansion ◽  
Luminosity Distance ◽  
Modern Cosmology ◽  
History Of ◽  
Expansion Of The Universe ◽  
The Universe

Expansion dynamics of the Universe is an important subject in modern cosmology. The dark energy equation of state determines these dynamics so that the Universe is in an accelerating phase. However, dark matter (DM) can also affect the accelerated expansion of the Universe through its equation of state. In the present work, we explore the expansion dynamics of the Universe in the presence of DM pressure. In this regard, applying the DM equation of state from the observational data related to the rotational curves of galaxies, we calculate the evolution of DM density. Moreover, the Hubble parameter, history of scale factor, luminosity distance, and deceleration parameter are studied while the DM pressure is taken into account. Our results verify that the DM pressure leads to higher values of the Hubble parameter at each redshift and the expansion of the Universe grows due to the DM pressure.

scholarly journals Cosmic Evolution of Holographic Dark Energy in f(G,T) Gravity

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
M. Sharif ◽  
Ayesha Ikram
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Phase Plane ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Momentum Tensor ◽  
Chaplygin Gas ◽  
Cosmic Evolution ◽  
Evolutionary Trajectories ◽  
The Universe

The aim of this paper is to analyze the cosmological evolution of holographic dark energy in f(G,T) gravity (G and T represent the Gauss-Bonnet invariant and trace of the energy-momentum tensor, respectively). We reconstruct f(G,T) model through correspondence scheme using power-law form of the scale factor. The qualitative analysis of the derived model is investigated with the help of evolutionary trajectories of equation of state and deceleration as well as state-finder diagnostic parameters and ωGT-ωGT′ cosmological phase plane. It is found that the equation of state parameter represents phantom epoch of the Universe whereas the deceleration parameter illustrates the accelerated phase. The state-finder plane corresponds to Chaplygin gas model while the freezing region is attained in ωGT-ωGT′ plane.

scholarly journals Bulk viscosity in F(T, TG) gravity

2017 ◽  
Vol 95 (3) ◽  
pp. 262-266
Author(s):  
M. Sharif ◽  
Kanwal Nazir
Keyword(s):  
Equation Of State ◽  
Bulk Viscosity ◽  
State Parameter ◽  
Time Dependent ◽  
Effective Equation ◽  
Phantom Divide ◽  
Equation Of State Parameter ◽  
Phantom Divide Line ◽  
Dependent Viscosity ◽  
The Universe

The present paper is devoted to exploring the effect of bulk viscosity in the context of F(T, TG) gravity. We consider a time-dependent viscosity model with a particular expression of Hubble parameter. We evaluate viscous effective equation of state parameter for three well-known F(T, TG) models. The behavior of the accelerated expanding universe is explored graphically through the viscous equation of state parameter. This parameter indicates the phantom-dominated era as well as crosses the phantom divide line for all three models. We conclude that the universe shows a transition from quintessence to phantom region in the presence of bulk viscosity.

scholarly journals Barrow HDE model for statefinder diagnostic in FLRW universe

2021 ◽  
pp. 2150030
Author(s):  
Anirudh Pradhan ◽  
Archana Dixit ◽  
Vinod Kumar Bhardwaj
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Density Parameter ◽  
Phantom Divide ◽  
Phantom Divide Line ◽  
Expansion Of The Universe ◽  
Flrw Universe ◽  
The Universe

We have analyzed the Barrow holographic dark energy (BHDE) in the framework of flat FLRW universe by considering the various estimations of Barrow exponent △. Here, we define BHDE, by applying the usual holographic principle at a cosmological system, for utilizing the Barrow entropy rather than the standard Bekenstein–Hawking. To understand the recent accelerated expansion of the universe, consider the Hubble horizon as the IR cutoff. The cosmological parameters, especially the density parameter [Formula: see text], the equation of the state parameter [Formula: see text], energy density [Formula: see text] and the deceleration parameter [Formula: see text] are studied in this paper and found the satisfactory behaviors. Moreover we additionally focus on the two geometric diagnostics, the statefinder [Formula: see text] and [Formula: see text] to discriminant BHDE model from the [Formula: see text]CDM model. Here we determined and plotted the trajectories of evolution for statefinder [Formula: see text], [Formula: see text] and [Formula: see text] diagnostic plane to understand the geometrical behavior of the BHDE model by utilizing Planck 2018 observational information. Finally, we have explored the new Barrow exponent △, which strongly affects the dark energy equation of state that can lead it to lie in the quintessence regime, phantom regime and exhibits the phantom-divide line during the cosmological evolution.

scholarly journals RECONSTRUCTION OF MODIFIED GRAVITY WITH GHOST DARK ENERGY MODELS

2012 ◽  
Vol 27 (18) ◽  
pp. 1250100 ◽  
Author(s):  
A. KHODAM-MOHAMMADI ◽  
M. MALEKJANI ◽  
M. MONSHIZADEH
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Modified Gravity ◽  
Deceleration Parameter ◽  
Accelerated Expansion ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Generalized Ghost Dark Energy

In this work, we reconstruct the f(R) modified gravity for different ghost and generalized-ghost dark energy (DE) models in FRW flat universe, which describes the accelerated expansion of the universe. The equation of state and deceleration parameter of reconstructed f(R) gravity have been calculated. The equation of state and deceleration parameter of reconstructed f(R)-ghost/generalized-ghost DE, have been calculated. We show that the corresponding f(R) gravity of ghost/generalized-ghost DE model can behave like phantom or quintessence. Also the transition between deceleration to acceleration regime is indicated by deceleration parameter diagram for reconstructed f(R) generalized-ghost DE model.

scholarly journals Einstein-Cartan gravity with scalar-fermion interactions

Open Physics ◽  
2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Olga Razina ◽  
Yerlan Myrzakulov ◽  
Nurzhan Serikbayev ◽  
Gulgasyl Nugmanova ◽  
Ratbay Myrzakulov
Keyword(s):  
Exact Analytical Solution ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Fermionic Field ◽  
Dirac Equations ◽  
Λcdm Model ◽  
Equation Of State Parameter ◽  
Expansion Of The Universe ◽  
Cartan Theory ◽  
The Universe

AbstractIn this paper, we have considered the g-essence and its particular cases, k-essence and f-essence, within the framework of the Einstein-Cartan theory. We have shown that a single fermionic field can give rise to the accelerated expansion within the Einstein-Cartan theory. The exact analytical solution of the Einstein-Cartan-Dirac equations is found. This solution describes the accelerated expansion of the Universe with the equation of state parameter w = −1 as in the case of ΛCDM model.

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