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Recent observations from the Dark Energy Spectroscopic Instrument (DESI 2025) indicate a weakening of cosmic acceleration at low redshifts $z < 1$, with effective dark energy equation of state parameters $w_0 > -1$ and $w_a < 0$. We…

Cosmology and Nongalactic Astrophysics · Physics 2025-03-28 John W. Moffat

We investigate the late time acceleration of the universe in the context of the Stephani model. This solution generalizes those of Friedmann-Lemaitre-Robertson-Walker (FLRW) in such a way that the spatial curvature is a function of of time.…

General Relativity and Quantum Cosmology · Physics 2015-02-26 S. Sedigheh. Hashemi , S. Jalalzadeh , N. Riazi

Assuming a flat Friedmann-Robertson-Walker cosmology with a single perfect fluid, we propose a pressure-density ratio that evolves as a specific universal function of the scale parameter. We show that such a ratio can indeed be consistent…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Golam Mortuza Hossain , Parthasarathi Majumdar

In this study, we have explored a transitioning cosmological model of universe's expansion in $f(R,\mathcal{L}_{m})$ gravity. The quadratic type of equation of state parameter in the form $\omega=-1 + \alpha (1 + z) + \beta (1 + z)^2$,…

General Relativity and Quantum Cosmology · Physics 2025-04-16 Vinod Kumar Bhardwaj , Saibal Ray

In recent years different explanations are provided for both an inflation and a recent acceleration in the expansion of the universe. In this Letter we show that a model of physical interest is the modification of general relativity with a…

High Energy Physics - Theory · Physics 2010-04-05 Ishwaree P. Neupane , Benedict M. N. Carter

In the present article, we developed a dynamical system in the context of modified $f(R,G,T)$ gravity, where $R$, $G$ and $T$ are Ricci scalar, Gauss-Bonnet term and energy-momentum tensor respectively. Development of the dynamical system…

General Relativity and Quantum Cosmology · Physics 2025-05-30 Elangbam Chingkheinganba Meetei , S. Surendra Singh

We present a complete analysis of the observational constraints and cosmological implications of our Bound Dark Energy (BDE) model aimed to explain the late-time cosmic acceleration of the universe. BDE is derived from particle physics and…

Cosmology and Nongalactic Astrophysics · Physics 2019-05-15 Erick Almaraz , Axel de la Macorra

The model-independent method of using type Ia supernovae proposed and developed by Daly and Djorgovski (2003, 2004) has been applied to the Riess et al. (2007) supernovae sample. Assuming only a Robertson-Walker metric, we find that the…

Astrophysics · Physics 2008-11-26 Ruth A. Daly , S. G. Djorgovski

We construct cosmological model in nonmetricity scalar functional gravitational Lagrangian $f(Q)$ which describes the dynamical evolution of the late accelerating universe. Cosmological models are constructed considering different…

General Relativity and Quantum Cosmology · Physics 2025-04-23 Bikash Chandra Roy , Aroonkumar Beesham , Bikash Chandra Paul

We investigate the possibility that the late acceleration observed in the rate of expansion of the universe is due to vacuum quantum effects arising in curved spacetime. The theoretical basis of the vacuum cold dark matter (VCDM), or vacuum…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Leonard Parker , Daniel A. T. Vanzella

We consider a physically viable cosmological model that has a field dependent Gauss-Bonnet coupling in its effective action, in addition to a standard scalar field potential. The presence of such terms in the four dimensional effective…

High Energy Physics - Theory · Physics 2008-11-26 Ishwaree P Neupane , Benedict M N Carter

In this article, we study a flat homogeneous FLRW model in Lyra geometry which is described by a time-dependent displacement vector. We consider an appropriate parametrization of the energy density of scalar field $ \rho_\phi $ in terms of…

General Relativity and Quantum Cosmology · Physics 2023-04-04 J. K. Singh , Shaily , Shri Ram , Joao R. L. Santos , Jéferson A. S. Fortunato

In this paper, we study the $f(T,\mathcal{T})$ gravity model in the presence of the bulk viscosity by the flat-FRW metric. The field equation is obtained by teleparallel gravity with tetrad field. The universe components are considered as…

General Relativity and Quantum Cosmology · Physics 2020-12-18 T. Mirzaei-Rezaei , Alireza Amani , E. Yusofi , S. Rouhani , M. A. Ramzanpour

In this work we consider a cosmological scenario in which the Universe contracts initially having a bouncing-like behavior, and accordingly after it bounces off, it decelerates following a matter dominated like evolution and at very large…

General Relativity and Quantum Cosmology · Physics 2020-12-02 S. D. Odintsov , V. K. Oikonomou , Tanmoy Paul

To explain the acceleration of the cosmological expansion researchers have considered an unusual form of mass-energy generically called dark energy. Dark energy has a ratio of pressure over mass density which obeys $w=p/\rho <-1/3$. This…

High Energy Physics - Theory · Physics 2008-12-19 Max Chaves , Douglas Singleton

In this paper, a bouncing cosmological scenario is studied in the background of a flat FLRW model with a specific parametrized hyperbolic form of scale factor $ a $ in terms of $ t $, where $ \lambda $ is taken as the model parameter. This…

General Relativity and Quantum Cosmology · Physics 2022-08-12 J. K. Singh , Shaily , Kazuharu Bamba

In the recently suggested modified non-metricity gravity theory with boundary terms in a flat FLRWspacetime universe, dark energy scenarios of cosmological models are examined in this study. An arbitrary function, $f(Q, C)=Q+{\alpha}C^{2}$,…

General Relativity and Quantum Cosmology · Physics 2023-10-05 Anirudh Pradhan , Archana Dixit , M. Zeyauddin , S. Krishnannair

In this paper, a new class of string and holographic dark energy (HDE) cosmological model in the context of the $f(R)$ theory of gravity using the Kasner metric is considered. The exact solution of the field equations is obtained using the…

General Relativity and Quantum Cosmology · Physics 2024-10-22 S. P. Hatkar , D. P. Tadas , A. S. Agrawal , S. D. Katore

In this paper we study the evolution of the dark energy parameter within the scope of a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model filled with barotropic fluid and dark energy by revisiting the recent results…

General Relativity and Quantum Cosmology · Physics 2015-05-01 Bijan Saha , Hassan Amirhashchi , Anirudh Pradhan

Some models within the framework of Gauss-Bonnet gravities are considered in the presence of a non-minimally coupled scalar field. By imposing a particular constraint on the scalar field coupling, an extension of the called…

General Relativity and Quantum Cosmology · Physics 2022-07-19 Sergei D. Odintsov , Diego Saez-Chillon Gomez , German S. Sharov