Article
Physics, Particles & Fields
Christian G. Bohmer, Erik Jensko, Ruth Lazkoz
Summary: When considering a homogeneous and isotropic cosmological model, the field equations of modified gravity theories can be transformed into autonomous differential equations, which is a successful approach to study such models. We propose a perspective that is applicable to many different modified gravity models and relies on the standard cosmological density parameters, allowing for the extraction of generic information before considering a specific model.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
A. Costantini, E. Elizaide
Summary: This study extends the investigation of unimodular Einsteinian gravity in the context of F(R) gravities for constructing anisotropic evolution scenarios. By imposing the unimodular constraint, the metric can be redefined and the desired evolution equations can be obtained. The reconstruction method is demonstrated with characteristic examples.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Xue-Zheng Zhu, Yang Yu, Xian Gao
Summary: We investigated scalar perturbations in a spatially covariant gravity theory with a dynamical lapse function. We found that the presence of the velocity of the lapse function gives rise to two scalar degrees of freedom. By integrating out the heavy mode and deriving the effective theory for the single light field, we obtained the solution to the single mode in the form of plane waves. We calculated the corrections to the power spectrum of the light mode from the heavy mode and found a power law mode for the coupled system in large scales when the two fields are not weakly coupled.
Article
Physics, Multidisciplinary
G. Mustafa, Abdelghani Errehymy, S. K. Maurya, M. K. Jasim, Allah Ditta
Summary: This manuscript explores the physical aspects of compact stars in f(tau, T) gravity using the Karori-Barua spacetime. It considers three specific compact star models and examines their physical acceptability through calculations and graphical analyses. The results show that the obtained solutions are physically viable and have good properties.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Renata Ferrero, Roberto Percacci
Summary: This research presents a general effective dynamics for diffeomorphisms of spacetime in a fixed external metric, which has subtly different properties at both kinematical and dynamical levels compared to familiar models. The energy-momentum (EM) tensor consists of two independently conserved parts, with the background solution being the identity diffeomorphism. The EM tensor of this solution leads to an effective cosmological constant.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Physics, Multidisciplinary
Rabia Saleem, Shan Ali, M. Israr Aslam
Summary: This paper investigates the cosmological implications of Rastall gravity by using the new Tsallis agegraphic dark energy (NTADE) and Sharma-Mittal holographic dark energy (SMHDE) models. The results show that the equation of state parameter for NTADE lies in the phantom region, while for SMHDE it exhibits quintom and quintessence regions dependent on the model parameter delta. The deceleration parameter shows a phase transition from decelerating to accelerating phases for both models. The omega(D) - omega(D)' pair exhibits freezing and thawing regions for NTADE, and freezing region for SMHDE. The (J, s) pair for SMHDE indicates different dark energy eras, including phantom, quintessence, and Chaplygin gas, while the NTADE model only shows Chaplygin gas behavior. It is concluded that SMHDE is a more efficient model as it approaches the Lambda CDM limit and produces results within a stable region according to graphical analysis of the square speed of sound.
CHINESE JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Genly Leon, Andronikos Paliathanasis
Summary: In the context of the modified teleparallel f(T, B) theory of gravity, this study considers the Kantowski-Sachs line element to describe a homogeneous and anisotropic background geometry, deriving field equations and investigating the existence of exact solutions, as well as studying the evolution of trajectories for the field equations.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Physics, Multidisciplinary
Y. Aditya, K. D. Raju, P. J. Ravindranath, D. R. K. Reddy
Summary: This article investigates a spatially homogeneous and anisotropic Bianchi type VI0 cosmological model with dark energy fluid and a massive scalar field in Einstein's theory of gravitation. The field equations are solved under specific conditions, leading to the evaluation of cosmological parameters and discussion of their dynamical aspects with reference to the accelerated expansion of the universe.
INDIAN JOURNAL OF PHYSICS
(2021)
Article
Physics, Multidisciplinary
M. Sharif, K. Hassan
Summary: This paper examines the complexity factor for dynamical anisotropic spheres in the framework of f(G, T) gravity, evaluating structure scalars and discussing dissipative and non-dissipative scenarios. The presence of dark source terms in f(G, T) gravity increases the complexity of the system.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Adria Gomez-Valent, Prajwal Hassan Puttasiddappa
Summary: Recent studies suggest that the Brans-Dicke cosmology with constant vacuum energy density might alleviate tensions found in the concordance cosmological model. Analyses in these studies indicate a preference for gravitational coupling values larger than Newton's constant, and improvements in cosmological datasets rely on mechanisms capable of screening modified gravity effects. Extensions of this cosmology show potential to maintain cosmological evolution while screening Brans-Dicke effects, but may struggle to explain significant departures from local measurements of gravitational coupling.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Optics
Yang Ge, Marcos Rigol
Summary: In finite systems driven across topological phase transitions, the Chern number and Bott index exhibit different behaviors depending on boundary conditions and lattice commensurability. The scaling of the fields at which these indices change shows Landau-Zener and near-adiabatic regimes based on drive speed and system size. The dc Hall response can detect topological phase transitions independently of the behavior of the topological indices.
Article
Physics, Particles & Fields
Allah Ditta, Ibrar Hussain, G. Mustafa, Abdelghani Errehymy, Mohammed Daoud
Summary: This study explores the physical aspects of wormhole geometry under embedded class-1 spacetime in f (T, tau) gravity, deriving solutions and calculating shape functions that can be used in other modified theories. Validity regions of energy conditions are analyzed, confirming the presence of exotic matter due to violation of the null energy condition.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Santosh V. Lohakare, B. Mishra, S. K. Maurya, Ksh. Newton Singh
Summary: In this study, the parametrization approach was used to recreate cosmological models, allowing for the incorporation of observational data. The results showed a transition from a decelerating to an accelerating stage of cosmic evolution, driven by quintessence dark energy. The violation of the strong energy conditions and the age of the Universe were also investigated.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Multidisciplinary
M. Ilyas, Aftab Ahmad, Fawad Khan, M. Wasif
Summary: In this paper, the authors investigate the effects of perfect fluid models and extended f(R, G, T) gravity on the flat Friedmann-Lematre-Robertson-Walker metric. They focus on exploring finite-time future singularities in late-time cosmic accelerating phases using specific f(R, G, T) models. The authors also consider the most recent estimated values for various parameters to examine the viability and bounds of the models induced by different energy conditions.
Article
Astronomy & Astrophysics
J. Ambjorn, Z. Drogosz, A. Gorlich, J. Jurkiewicz
Summary: The study reveals that the geometry of a quantum universe with a four-torus topology consists of a small semiclassical toroidal bulk part surrounded by many outgrowths with almost spherical topologies, yet still quite fractal.
Article
Physics, Multidisciplinary
Francisco Tello-Ortiz, B. Mishra, A. Alvarez, Ksh. Newton Singh
Summary: This article presents new wormhole solutions in the framework of General Relativity. By utilizing minimal geometric deformation approach and noncommutative geometry density profiles, new asymptotically wormhole solutions are obtained. By constraining parameters, the energy-momentum tensor and positive density are obtained.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
Article
Physics, Mathematical
S. A. Kadam, Jackson Levi Said, B. Mishra
Summary: In this paper, the field equations of f(T, B) gravity were explored as an extension of teleparallel gravity in an isotropic and homogeneous space-time. The dynamical parameters were derived using the power law and exponential scale factor function. The models exhibited accelerating behavior and approached lambda CDM at late time. The violation of the strong energy condition was established in both models.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
Santosh V. Lohakare, B. Mishra, S. K. Maurya, Ksh. Newton Singh
Summary: In this study, the parametrization approach was used to recreate cosmological models, allowing for the incorporation of observational data. The results showed a transition from a decelerating to an accelerating stage of cosmic evolution, driven by quintessence dark energy. The violation of the strong energy conditions and the age of the Universe were also investigated.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Multidisciplinary
S. A. Narawade, M. Koussour, B. Mishra
Summary: This paper presents an accelerating cosmological model in flat and anisotropic space-time using extended symmetric teleparallel gravity. It employs a time variable deceleration parameter that exhibits early deceleration and late time acceleration in the form of a hybrid scale factor. The study analyzes the late time behavior of the Universe based on the best-fit values of the free parameters and establishes the importance of a hybrid scale factor in addressing the cosmic phenomena issue.
ANNALEN DER PHYSIK
(2023)
Article
Physics, Multidisciplinary
B. S. Goncalves, P. H. R. S. Moraes, B. Mishra
Summary: We have constructed a cosmological model based on the f(R, L-m) gravity theory, incorporating the Friedmann-Lemaitre-Robertson-Walker metric and the field equations. Our chosen function, R/16p + (1 + sR)L-m, includes a constant s representing the geometry-matter coupling. Our solutions are notable for evading the Big Bang singularity and accurately predicting cosmic acceleration without requiring the cosmological constant, due to the presence of geometry-matter coupling terms in the Friedmann-like equations.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
S. A. Kadam, B. Mishra, Jackson Levi Said
Summary: All degrees of freedom related to the torsion scalar can be explored using the f(T, T-G) gravity formalism for different forms of f(T, T-G). The Noether symmetry approach is used to select models and determine exact solutions for a Lagrangian. This study extends the analysis of Noether symmetries in gauss-bonnet-teleparallel cosmology and investigates different models and their nontrivial Noether vectors.
Article
Astronomy & Astrophysics
A. S. Agrawal, B. Mishra, S. K. Tripathy
Summary: In this paper, a cosmological model based on f(Q, T) gravity is presented and the parameters are constrained using cosmological data sets. The Hubble parameter is obtained in terms of redshift through algebraic manipulation. The model parameters are constrained using MCMC analysis with the most current Hubble and Pantheon+ data, and verified through the BAO data set. The model shows an early deceleration transitioning to an accelerating phase of the Universe, favored by a positive slope in the Om(z) diagnostic.
JOURNAL OF HIGH ENERGY ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Santosh Lohakare, Krishna Rathore, B. Mishra
Summary: This paper analyzes the geometrical and dynamical parameters of the F(R, G) = alpha R(2)G(beta) cosmological model and constrains the parameters through cosmological data sets. The results show that the model exhibits deceleration and acceleration in the radiation era and matter-dominated era respectively, while also restricting the value of the parameter beta. Additionally, the stability of the model is explored through the behavior of critical points, and the density parameter values for matter-dominated and dark energy components are obtained.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
A. S. Agrawal, S. Mishra, S. K. Tripathy, B. Mishra
Summary: In this study, we investigate bouncing cosmological models under the F(R) theory of gravity in an isotropic and homogeneous spacetime. Two functional forms of F(R) are studied, and their dynamical parameters and cosmographic parameters are derived and analyzed. The violation of the strong energy conditions in both bouncing models is demonstrated. It is shown that both models exhibit stable behavior with respect to cosmic time.
GRAVITATION & COSMOLOGY
(2023)
Article
Physics, Particles & Fields
S. A. Narawade, M. Koussour, B. Mishra
Summary: In this paper, we present an accelerating cosmological model based on extended symmetric teleparallel gravity or f(Q, T) gravity. The present values of cosmological and dynamical parameters are obtained using constraints from various datasets. The model shows quintessence behavior and its stability is validated through dynamical system analysis.
Article
Physics, Particles & Fields
A. S. Agrawal, B. Mishra, P. K. Agrawal
Summary: In this paper, we have presented the matter bounce scenario of the Universe within an extended symmetric teleparallel gravity, known as the f (Q) gravity. By incorporating the bouncing scenario and loop quantum cosmology, we have determined the form of the function f (Q) within the Friedmann-Lemaitre-Robertson Walker space-time. Considering a background cosmology dominated by dust fluid, we have expressed the e-folding parameter that includes the nonmetricity term. Due to the invalidity of the slow roll criterion in the bouncing context, we have utilized a conformal equivalence between f (Q) and scalar-tensor model to apply the bottom-up reconstruction technique. The dynamics of the model have been examined through phase space analysis, yielding both stable and unstable nodes. Furthermore, stability analysis has been performed on the first-order scalar perturbation of the Hubble parameter and matter energy density to confirm the stability of the model.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
L. K. Duchaniya, S. A. Kadam, Jackson Levi Said, B. Mishra
Summary: Teleparallel based cosmological models describe gravity by using torsion as the mediator of gravitation. In this study, the dynamical system analysis was done to investigate the cosmological behavior of f (T, phi) gravity, where T represents the torsion scalar and phi represents the scalar field. Two models with different functional forms of the torsion scalar were presented, and their critical points, stability behavior, and corresponding cosmology were analyzed. Graphical representations were used to show the equation of state parameter and density parameters for different phases of matter-dominated, radiation-dominated, and dark energy.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
L. K. Duchaniya, B. Mishra, Jackson Levi Said
Summary: In this study, the Noether Symmetry approach is used to investigate an extended teleparallel f(T,phi) gravity. The obtained exact cosmological solutions are consistent with the Noether symmetry.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Rahul Bhagat, S. A. Narawade, B. Mishra, S. K. Tripathy
Summary: The f(Q, T) cosmological model was used in this study to understand cosmic evolution. Through analyzing the datasets of Hubble, Pantheon, and BAO, constraints and parameter values of the model were obtained, and the fit between the model curve and the ΛCDM curve was examined. State finder diagnostics, energy conditions, and the Om(z) diagnostic were used to gain further insights into the properties of the model.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
S. A. Kadam, Ninaad P. Thakkar, B. Mishra
Summary: This paper performs a dynamical system analysis on cosmological models in extended teleparallel gravity, specifically f(T, B) gravity. The critical points and stability conditions are obtained for two different forms of f(T, B), and the evolution of standard density parameters and behavior of dark energy phase are also analyzed. The results indicate accelerating behavior for both models.
EUROPEAN PHYSICAL JOURNAL C
(2023)
