Article
Astronomy & Astrophysics
Yannan Qi, Weiqiang Yang, Yitao Wang, Chenchen Zhao, TianYi Han, Yabo Wu
Summary: This study investigates the late-time dynamics of the F(R) gravity model, focusing on the cosmological evolution and the implications from supernovae observations. Numerical solutions of the field equations reveal a phantom evolution and physically viable cosmology at late times with fine-tuned parameters. It is noteworthy that dark energy oscillations exist in this model, and simple F(R) gravity models can realize phantom, nearly de-Sitter, and quintessential dark energy eras without the need for phantom scalar fields or relativistic fluids.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
Bita Farsi, Ahmad Sheykhi
Summary: This study reveals the effects of an extra longitudinal degree of freedom on the evolution of perturbations in the context of mimetic gravity. By analyzing linear perturbations, it is found that the mimetic potential can act as dark energy and influence the dynamics of matter perturbations and cosmological parameters.
Article
Physics, Multidisciplinary
M. Zubair, Lala Rukh Durrani
Summary: This paper analyzes Tsallis holographic dark energy in a flat Friedmann-Robertson Walker model under the framework of f(R, T) gravity, studying the effects in a non interactive universe by taking different IR cut-offs. Different cosmological tools are used to study the cosmic evolution, and the impact of various parameters is analyzed. The models exhibit appropriate behavior for the system parameters and support accelerated expansion, showing stability for event horizon partially based on the speed of sound. Various diagnostic mechanisms are used to further examine the behavior of the model, with Om parameter supporting quintessence era and statefinder hierarchy effectively distinguishing the model from the ΛCDM model.
CHINESE JOURNAL OF PHYSICS
(2021)
Article
Physics, Multidisciplinary
J. K. Singh, Akanksha Singh, G. K. Goswami, J. Jena
Summary: We investigate a flat FLRW-model in f (R, T)-gravity, which shows accelerated expansion in the late-time Universe and is consistent with the standard cosmology Lambda CDM.
Article
Astronomy & Astrophysics
A. Oliveros
Summary: In this study, a reparametrization method for a viable f(R) gravity model is proposed to represent it as a perturbation of the Lambda CDM model. The results show that the proposed model is practically indistinguishable from the Lambda CDM model at the background level and exhibits excellent agreement with the numerical solution. By appropriately choosing the model parameters, the obtained cosmological parameters are consistent with observations and the predictions of the Lambda CDM model. Additionally, the anomalous behavior at high redshifts is avoided by utilizing an approximate analytical solution.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Astronomy & Astrophysics
Sergei D. Odintsov, Diego Saez-Chillon Gomez, German S. Sharov
Summary: This study analyses the cosmological evolution within the framework of exponential F(R) gravity by assuming two forms of dark matter: a standard dust-like fluid and an axion scalar field. It is found that the axion-like field can serve as dark matter when approaching the minimum of its potential. The models are compared with observational data, including supernovae, Hubble parameter estimations, acoustic oscillations, and cosmic microwave background distances, and show great potential in describing these observations when compared with the Lambda CDM model, supporting the viability of exponential F(R) gravity.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
Dinesh Chandra Maurya
Summary: In this study, dark energy scenarios in higher derivative f(R, L-m) gravity theory have been investigated. By constraining the cosmographic series of Hubble function with Hubble constant H (z) datasets, the effective dark energy properties of the universe have been explored. The results show that dark energy behaves like a time-dependent cosmological constant and the present age of the universe is estimated to be 14.28 billion years.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
Lakhan V. Jaybhaye, Snehasish Bhattacharjee, P. K. Sahoo
Summary: This paper aims to recreate the gravitational baryogenesis epoch in the framework of the f (R, Lm) theory of gravity, where R and Lm are the curvature scalar and the matter Lagrangian, respectively. We examine the model, f (R, Lm) = R2 + L & alpha;m + & zeta;, under the supposition that the universe is saturated with dark energy and perfect fluid, with a non-zero baryon to entropy ratio during a radiation dominance era. Our study found that f (R, Lm) gravity can considerably and steadily make a contribution to the phenomenon of gravitational baryogenesis. & COPY; 2023 Elsevier B.V. All rights reserved.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Multidisciplinary
Abdelghani Errehymy, Sunil Kumar Maurya, Sudan Hansraj, Mohammed Daoud, Haifa I. Alrebdi, Abdel-Haleem Abdel-Aty
Summary: In this paper, generalized Ellis-Bronikov traversable wormhole geometries for static and spherically symmetric spacetime in the background of f(R) gravity are explored. It is found that these wormholes are generated by dark matter galactic halos and violate the energy conditions, supporting their existence and traversability.
ANNALEN DER PHYSIK
(2023)
Article
Astronomy & Astrophysics
V. K. Oikonomou, Ifigeneia Giannakoudi
Summary: In this work, the late-time dynamics of several F(R) gravity models are studied. It is found that these models can achieve compatibility with the latest Planck constraints at late times by fine-tuning the parameters and providing a unified description of inflation and dark energy era. Furthermore, it is shown that F(R) gravity models generate a wide range of different dark energy physics, including phantom, nearly de Sitter, and quintessential dark energy eras, in contrast to general relativistic fluids and scalar field descriptions.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Multidisciplinary Sciences
Bofeng Wu
Summary: A signature invariant geometric algebra framework for spacetime physics is formulated in this paper, including techniques related to relative vector and spacetime split, as well as rotor techniques for Lorentz transformations and relativistic dynamics of a massive particle in curved spacetime. The paper also presents a three-dimensional analogue of Newton's second law for a particle in curved spacetime, and provides a geometric algebra approach to gyroscopic precession in Lense-Thirring spacetime for a gyroscope moving.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Particles & Fields
M. Z. Bhatti, S. Ijaz, Bander Almutairi, A. S. Khan
Summary: This paper analyzes the characteristics of a non-static sphere with an anisotropic fluid distribution in the background of modified f (G) theory. The presence of a conformal Killing vector allows for the computation of reliable results for the modified field equations. Various precise analytical solutions are obtained for both non-dissipative and dissipative systems by making different choices of the conformal Killing vector. The matching conditions in the context of f (G) gravity are computed and specific constraints are applied to determine significant results. The results of this study help in understanding the properties of astrophysical objects.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Beatrice Murorunkwere, Joseph Ntahompagaze, Edward Jurua
Summary: In this study, the 1+3 covariant approach and equivalence between f(R) gravity and scalar-tensor theory were applied to analyze cosmological perturbations. Focus was on dust dominated area with perturbation equations applied to a background solution of alpha R+beta R-n model, and the evolution of energy-density perturbations in a dust-dominated universe was found to decay with increasing redshift through numerical solutions.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Particles & Fields
Isil Basaran Oz, Kazuharu Bamba
Summary: This paper investigates the f(R) theory in static cylindrically symmetric and plane-symmetric spacetimes. Solutions to the field equations of these models are found using the Noether symmetry method, leading to the discovery of new solutions. Additionally, the GR limit for each case is examined.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Zahra Haghani
Summary: The theory considers the growth rate of matter perturbations in the Einstein dark energy theory, with three fixed points. Due to the presence of the trace of the energy-momentum tensor, these fixed points occur at different locations compared to the Lambda CDM theory.
EUROPEAN PHYSICAL JOURNAL C
(2021)