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In the generalized matter-geometry coupling theory, we investigate the physical characteristics and causality of some new cosmological models for a flat, homogeneous, and isotropic spacetime filled with stiff, radiation, dust, and curvature…

General Relativity and Quantum Cosmology · Physics 2025-04-10 Dinesh Chandra Maurya , Javlon Rayimbaev , Inomjon Ibragimov , Sokhibjan Muminov

A generalized version for the Rastall theory is proposed showing the agreement with the cosmic accelerating expansion. In this regard, a coupling between geometry and the pressureless matter fields is derived which may play the role of dark…

General Relativity and Quantum Cosmology · Physics 2017-05-24 H. Moradpour , Y. Heydarzade , F. Darabi , Ines G. Salako

Cosmological implications of a generalized Rastall theory where the non-conservation equation is promoted to accepts arbitrary functions of the Ricci scalar is considered. We have obtain the model parameters of the power-law ansatz…

General Relativity and Quantum Cosmology · Physics 2021-10-13 Shahab Shahidi

Using a new recently compiled milliarcsecond compact radio data set of 120 intermediate-luminosity quasars in the redshift range $0.46< z <2.76$, whose statistical linear sizes show negligible dependence on redshifts and intrinsic…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-30 Jing-Zhao Qi , Shuo Cao , Marek Biesiada , Xiaogang Zheng , Zong-Hong Zhu

In this work, we propose a scheme for cosmic evolution in a generalized Rastall gravity. In our approach, the role of dark energy is taken by the non-conserved sector of the stress energy-momentum tensor. The resultant cosmic evolution is…

General Relativity and Quantum Cosmology · Physics 2020-06-08 Kai Lin , Wei-Liang Qian

We use higher-redshift gamma-ray burst (GRB), HII starburst galaxy (HIIG), and quasar angular size (QSO-AS) measurements to constrain six spatially flat and non-flat cosmological models. These three sets of cosmological constraints are…

Cosmology and Nongalactic Astrophysics · Physics 2021-01-15 Shulei Cao , Joseph Ryan , Narayan Khadka , Bharat Ratra

A sample of quasars has been recently assembled to investigate the non-linear relation between their monochromatic luminosities at 2500{\AA}, and 2 keV and to exploit quasars as a new class of standardized candles. The use of this technique…

The existence of a dark energy component has usually been invoked as the most plausible way to explain the recent observational results. However, it is also well known that effects arising from new physics (e.g., extra dimensions) can mimic…

Astrophysics · Physics 2009-11-10 J. S. Alcaniz , Abha Dev , Deepak Jain

This is the third of a series of papers in which we derive simultaneous constraints on cosmological parameters and X-ray scaling relations using observations of the growth of massive, X-ray flux-selected galaxy clusters. Our data set…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 David Rapetti , Steven W. Allen , Adam Mantz , Harald Ebeling

Observational evidence for the accelerated expansion of the universe requires dark energy for its explanation if general relativity is an accurate model of gravity. However, dark energy is a mysterious quantity and we do not know much about…

Cosmology and Nongalactic Astrophysics · Physics 2022-04-14 Narayan Khadka

We investigate the imprints of the Generalized Uncertainty Principle on cosmological scales by using redshift-space distortion measurements in combination with background cosmological data to determine constraints on the deformation…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-03 Andronikos Paliathanasis

In this study, we have explored the cosmological dynamics of an isotropic, homogeneous universe in Rastall gravity. For this purpose, we use the parameterization of the EoS parameter in the form $\omega(z) = \frac{\omega_{0}}{(z+1)} $ to…

General Relativity and Quantum Cosmology · Physics 2026-02-10 Vinod Kumar Bhardwaj , Anil Kumar Yadav , Manish Kalra , Pankaj , Rajendra Prasad

Context. Explaining the accelerated expansion of the Universe is one of the fundamental challenges in physics today. Cosmography provides information about the evolution of the universe derived from measured distances, assuming only that…

Cosmology and Nongalactic Astrophysics · Physics 2016-10-05 Marek Demianski , Ester Piedipalumbo , Disha Sawant , Lorenzo Amati

A cyclic flat universe with quintom behaviour and future big rip has been presented in the framework of Rastall gravity, which is an extension of the standard $\Lambda$CDM model. The Hubble parameter oscillates periodically between positive…

General Relativity and Quantum Cosmology · Physics 2025-03-18 Nasr Ahmed , Anirudh Pradhan , Archana Dixit

In this research work, we explore the late-time accelerated expansion of the universe within the framework of modified gravity, specifically $f(R, L_m)$ theory, by considering two non-linear models: $f(R, L_{m}) = \frac{R}{2}+(1+\eta R)…

General Relativity and Quantum Cosmology · Physics 2025-06-23 Khomesh R. Patle , G. P. Singh , Romanshu Garg

In this work, we investigate the General Relativistic Entropic Acceleration (GREA) framework, in which late-time acceleration emerges from entropy production associated with the cosmological horizon, and compare its performance with the…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-03 Irene Graziotti , Chiara De Leo , Matteo Martinelli

Most cosmological constraints on modified gravity are obtained assuming that the cosmic evolution was standard $\Lambda$CDM in the past and that the present matter density and power spectrum normalization are the same as in a $\Lambda$CDM…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-22 Laura Taddei , Luca Amendola

It is well-known that allowing for spatial curvature affects constraints on cosmological parameters such as the dark energy equation of state parameters. Here we study the effect of curvature on constraints on parameters used to test…

Cosmology and Nongalactic Astrophysics · Physics 2013-05-30 Jason Dossett , Mustapha Ishak

We use observational data on the magnitude-redshift relation for Type Ia supernovae together with constraints on the ages of the oldest stars to rule out a higher-dimensional extension of General Relativity with a negative kinetic-energy…

General Relativity and Quantum Cosmology · Physics 2016-05-25 James Overduin , Nathan Prins , Joohan Lee

We propose to use relative galaxy ages as a means of constraining cosmological parameters. By measuring the age difference between two ensembles of old galaxies at somewhat different redshifts, one could determine the derivative of redshift…

Astrophysics · Physics 2009-11-06 Raul Jimenez , Abraham Loeb