scholarly journals Generic feature of future crossing of phantom divide in viablef(R) gravity models

2010 ◽  
Vol 2010 (11) ◽  
pp. 001-001 ◽  
Author(s):  
Kazuharu Bamba ◽  
Chao-Qiang Geng ◽  
Chung-Chi Lee
Keyword(s):  
Gravity Models ◽  
Phantom Divide ◽  
Crossing Of Phantom Divide

scholarly journals VISCOUS DARK ENERGY IN f(T) GRAVITY

2013 ◽  
Vol 28 (27) ◽  
pp. 1350118 ◽  
Author(s):  
M. SHARIF ◽  
SHAMAILA RANI
Keyword(s):  
Dark Energy ◽  
Graphical Representation ◽  
Teleparallel Gravity ◽  
Eos Parameter ◽  
Phantom Divide ◽  
Accelerating Expansion ◽  
Phantom Divide Line ◽  
Expansion Of The Universe ◽  
Crossing Of Phantom Divide ◽  
The Universe

We study the bulk viscosity taking dust matter in the generalized teleparallel gravity. We consider different dark energy (DE) models in this scenario along with a time-dependent viscous model to construct the viscous equation of state (EoS) parameter for these DE models. We discuss the graphical representation of this parameter to investigate the viscosity effects on the accelerating expansion of the universe. It is mentioned here that the behavior of the universe depends upon the viscous coefficients showing the transition from decelerating to accelerating phase. It leads to the crossing of phantom divide line and becomes phantom dominated for specific ranges of these coefficients.

scholarly journals CROSSING OF PHANTOM DIVIDE IN F(R) GRAVITY

2010 ◽  
Vol 25 (11n12) ◽  
pp. 900-908 ◽  
Author(s):  
KAZUHARU BAMBA ◽  
CHAO-QIANG GENG ◽  
SHIN'ICHI NOJIRI ◽  
SERGEI D. ODINTSOV
Keyword(s):  
Explicit Model ◽  
Phantom Divide ◽  
Big Rip ◽  
Crossing Of Phantom Divide ◽  
Reconstructed Model

An explicit model of F(R) gravity with realizing a crossing of the phantom divide is reconstructed. In particular, it is shown that the Big Rip singularity may appear in the reconstructed model of F(R) gravity. Such a Big Rip singularity could be avoided by adding R2 term or non-singular viable F(R) theory1 to the model because phantom behavior becomes transient.

Role of collisional matter in the framework of extended teleparallel theory

2020 ◽  
Vol 29 (15) ◽  
pp. 2050099
Author(s):  
Muhammad Zeeshan ◽  
M. Zubair ◽  
Rabia Saleem
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Power Law ◽  
Phantom Divide ◽  
Evolutionary Scenario ◽  
Cosmic Evolution ◽  
Phantom Divide Line ◽  
Teleparallel Theory ◽  
Crossing Of Phantom Divide

The purpose of this work is to examine the cosmic evolution in the presence of collisional matter (CM) with and without radiations in a modified Teleparallel theory involving a generic function [Formula: see text] which depends on the scalar torsion [Formula: see text] and the boundary term associated to the divergence of torsion [Formula: see text]. We select seven novel [Formula: see text] models including power law, logarithmic models and exponential models, some of these reported in [S. Bahamonde, M. Zubair and G. Abbas, Phys. Dark Univ. 19 (2018) 78; S. Bahamonde and S. Capozziello, The Eur. Phys. J. C. 77 (2017) 107; C. Escamilla-Rivera and J. L. Said, Class. Quantum Grav. 37 (2020) 165002] and discuss the evolutionary scenario. The behavior of deceleration parameter [Formula: see text], Hubble parameter [Formula: see text], Equation-of-state (EoS) for dark energy (DE) and effective EoS is presented. [Formula: see text]CDM epoch and crossing of phantom divide line (approaching to phantom era) is observed in scenarios like noncollisional matter (NCM) with radiation, CM with and without radiation. Results are found to be adequate with recent cosmic observations.

Observations favor the crossing of phantom divide lines

2010 ◽  
Vol 53 (3) ◽  
pp. 562-566 ◽  
Author(s):  
TieTie Huang ◽  
PuXun Wu ◽  
HongWei Yu
Keyword(s):  
Phantom Divide ◽  
Crossing Of Phantom Divide

Phantom crossing with collisional matter in f(T) gravity

2016 ◽  
Vol 25 (05) ◽  
pp. 1650057 ◽  
Author(s):  
M. Zubair
Keyword(s):  
Dark Energy ◽  
Late Time ◽  
Eos Parameter ◽  
Phantom Divide ◽  
Phantom Crossing ◽  
Phantom Divide Line ◽  
C 71 ◽  
Scalar Theories ◽  
The One ◽  
Crossing Of Phantom Divide

We study the late-time cosmological evolution of [Formula: see text] (where [Formula: see text] is the torsion scalar) theories with matter contents consisting of collisional self-interacting matter and radiations. The power law, exponential and logarithmic [Formula: see text] models are considered to explore the evolution of Hubble parameter [Formula: see text], dark energy (DE) equation of state (EoS) [Formula: see text] and effective EoS parameter [Formula: see text]. We show that crossing of phantom divide line can be realized in the presence of collisional matter as compared to the results obtained for the choice of noncollisional matter [K. Bamba, C.-Q. Geng, C.-C. Lee and L.-W. Luo, J. Cosmol. Astropart. Phys. 01 (2011) 021; K. Bamba, C.-Q. Geng and C.-C. Lee, arXiv:1008.4036]. The evolutionary behavior of [Formula: see text] is consistent with the one developed in [P. Wu and H. Yu, Eur. Phys. J. C 71 (2011) 1552] and recent observational data [U. Alam, V. Sahni and A. A. Starobinsky, J. Cosmol. Astropart. Phys. 0406 (2004) 008; S. Nesseris and L. Perivolaropoulos, J. Cosmol. Astropart. Phys. 0701 (2007) 018; P. Wu and H. Yu, Phys. Lett. B 643 (2006) 315; U. Alam, V. Sahni and A. A. Starobinsky, J. Cosmol. Astropart. Phys. 0702 (2007) 011; H. K. Jassal, J. S. Bagla and T. Padmanabhan, Mon. Not. R. Astron. Soc. 405 (2010) 2639].

scholarly journals PHANTOM CROSSING IN VIABLE f(R) THEORIES

2011 ◽  
Vol 20 (08) ◽  
pp. 1339-1345 ◽  
Author(s):  
KAZUHARU BAMBA ◽  
CHAO-QIANG GENG ◽  
CHUNG-CHI LEE
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Modified Gravity ◽  
Gravity Models ◽  
Phantom Divide ◽  
The Past ◽  
Modified Gravity Theories ◽  
Phantom Crossing ◽  
Gravity Theories

We review the equation of state for dark energy in modified gravity theories. In particular, we summarize the generic feature of the phantom divide crossing in the past and future in viable f(R) gravity models.

scholarly journals COSMOLOGICAL ASPECTS OF A VECTOR FIELD MODEL

2012 ◽  
Vol 21 (07) ◽  
pp. 1250063 ◽  
Author(s):  
S. DAVOOD SADATIAN
Keyword(s):  
Vector Field ◽  
Field Model ◽  
Lorentz Invariance ◽  
Normal Vector ◽  
Normal Vector Field ◽  
Phantom Divide ◽  
Invariance Violation ◽  
Phantom Divide Line ◽  
Brane Models ◽  
Crossing Of Phantom Divide

We have studied a DGP-inspired braneworld scenario where the idea of Lorentz invariance violation has been combined into a specifying preferred frame that embed a dynamical normal vector field to brane. We propose the Lorentz violating DGP brane models with enough parameters can explain crossing of phantom divide line. Also we have considered the model for proper cosmological evolution that is according to the observed behavior of the equation of state. In other view point, we have described a Rip singularity solution of model that occur in this model.

Determinants of Brazilian Exports by Levels of Technological Intensity: A Gravity Model Analysis Using the PPML Estimator

2019 ◽  
Vol 10 (9) ◽  
pp. 861-879
Author(s):  
Edson Roberto Vieira ◽  
◽  
Daniel Henrique Alves Reis ◽  
Keyword(s):  
International Market ◽  
Positive Influence ◽  
Gravity Models ◽  
Transport Costs ◽  
Consumer Market ◽  
Technology Products ◽  
The Us ◽  
Trading Partners ◽  
Negative Impacts ◽  
Technological Intensity

The objective of this study is to analyze the determinants of Brazilian exports by levels of technological intensity in the period 2000-2015. Gravity models were estimated for total of the exports and for each type of exports by levels of technological intensity, using the PPML-estimator. The study indicates that there is a process of concentration of Brazilian exports in low technology and medium-low technology products, at the same period in which China's share of total Brazilian shipments abroad grew. Estimates of empirical gravity models have shown that the income and size of the consumer market of Brazil’s trading partners seem to have the greatest positive influence on the Brazilian exports. Indications of this study are that the Brazil should continue to diversify its trading partners to minimize the impacts of a possible reduction of the economic growth of large trading partners (such as China and the US) on its exports and increase its exports of products with greater technological intensity. The results also highlight the need for Brazil to make greater efforts to increase its competitiveness in the international market to reduce the negative impacts of transport costs on the final prices of products exported by the country.

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