Article
Astronomy & Astrophysics
Damianos Iosifidis, Nurgissa Myrzakulov, Ratbay Myrzakulov
Summary: The study derived the field equations for the metric-affine version of the Myrzakulov gravity model and extended the theory to a broader range. It considered gravitational Lagrangians and linear cases, obtaining modified Friedmann equations in a cosmological setup. The focus on vanishing non-metricity sector and matter coupled to torsion led to a complete set of equations describing cosmological behavior along with solutions.
Article
Astronomy & Astrophysics
Rui-Hui Lin, Xiang-Hua Zhai
Summary: General relativity can be formulated equivalently with a non-Riemannian geometry involving a nonmetricity Q but vanishing curvature R and torsion T. Modification based on this description leads to f(Q) gravity. The application of f(Q) gravity to spherically symmetric configurations is explored, demonstrating effects on external and internal solutions of compact stars through different modifications.
Article
Multidisciplinary Sciences
Polina Petriakova, Arkady Popov, Sergey Rubin
Summary: Studying the evolution of the Universe from sub-Planckian scale to present times reveals the requirement for exponential expansion of space and significant restrictions on parameter values of a function f(R). The initial metric of the Universe is assumed to be maximally symmetric with positive curvature.
Article
Physics, Multidisciplinary
Amir H. Rezaei, T. Azizi, N. Rashidi
Summary: In this paper, an exponential form of modified gravity is considered. The theory is consistent with local tests and various aspects of the model are investigated, including the static solution, scalar field potential, and stability of critical points. The realization of inflation and its graceful exit in this model are also studied.
Article
Physics, Multidisciplinary
Z. Yousaf, M. Z. Bhatti, A. Ali
Summary: This article explores the effects of extra curvature terms on the dynamics of evolving fluid for charged fluid in the context of f(R, T) theory. By evaluating complexity, self-gravitating objects satisfying quasi-homologous constraint and zero complexity factor are identified, and Maxwell-f(R, T) gravitation equations are formulated. The complexity factor Y-TF, obtained through orthogonal decomposition of the Riemann curvature tensor, includes contributions of charge and f(R, T) terms, leading to increased complexity in the self-gravitating system.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Physics, Multidisciplinary
Riaz Ahmed, G. Abbas, Ertan Gudekli
Summary: This study investigates the dissipative gravitational collapse of an anisotropic spherically symmetric radiating star in f(R, T) gravity, while confirming the well-behaved energy conditions and other physical properties in the background of f(R, T) theory. The results of the model are consistent with General Relativity when the parameter lambda is set to zero.
CHINESE JOURNAL OF PHYSICS
(2021)
Review
Astronomy & Astrophysics
Muhammad Zahid Mughal, Iftikhar Ahmad, Juan Luis Garcia Guirao
Summary: This review article discusses the development of relativistic cosmology and the introduction of inflation as an exponentially expanding early phase of the universe. It also explores how the inflationary paradigm solves cosmological issues by proposing a fast expansion period in the early universe. Further discussions include inflation and dark energy in f(R) modified gravity.
Article
Astronomy & Astrophysics
Jafar Sadeghi, Behnam Pourhassan, Saeed Noori Gashti, Elaheh Naghd Mezerji, Antonio Pasqua
Summary: In this study, the inflationary scenario in logarithmic f (R) gravity is examined, with a focus on the constant-roll rate of inflation. The cosmic evolution of the logarithmic f (R) gravity is investigated using constant-roll conditions, and numerical and graphical analyses are presented. The resulting potential satisfying the constant-roll conditions is obtained and tested against the refined swampland conjecture and the latest observable data.
Article
Physics, Multidisciplinary
J. A. Astorga-Moreno, E. A. Mena-Barboza
Summary: Modified gravity theories have gained significant attention in the past decade. This study utilizes deformed phase space in f(R) gravity to derive the Wheeler-DeWitt equation in the Quantum Cosmology scenario for a Friedmann-Lemaitre-Robertson-Walker model. Furthermore, a function f(R) that corresponds to the -Cold Dark Matter model is also considered.
Article
Physics, Multidisciplinary
S. Das, G. Lambiase, E. C. Vagenas
Summary: Virtual D-branes offer a possibility for describing quantum gravitational fluctuations of the spacetime background, which may lead to a minor violation of Lorentz invariance (and possibly the equivalence principle). Within this framework, the formation of light elements in the early Universe (Big Bang Nucleosynthesis) is studied. Utilizing observations from Big Bang Nucleosynthesis, an upper limit of topological fluctuations in the spacetime foam vacuum s(2) is inferred to be s(2 )≤ 10(-22).
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Multidisciplinary
J. K. Singh, Akanksha Shaily, Akanksha Singh, Aroonkumar Beesham, Hamid Shabani
Summary: We investigate the realization of a bounce in the framework of higher order curvature in f(R, T) modified theory of gravity. Our analysis focuses on explaining the contraction phase, bounce phase, and expansion phase using cosmological parameters. We find a violation of the null energy condition, model instability, and a singularity at the bouncing point, supporting the concept of a bouncing cosmology. The equation of state parameter exhibits a ghost condensate behavior near the bouncing point. Additionally, we discuss the stability of the model through linear perturbations in the Hubble parameter and energy density.
Article
Astronomy & Astrophysics
Santosh V. Lohakare, Francisco Tello-Ortiz, S. K. Tripathy, B. Mishra
Summary: In this paper, the bouncing behavior of cosmological models in the background of the Hubble function in the F(R,G) theory of gravity was studied. It was found that both models satisfy the bouncing cosmological properties and exhibit accelerating behavior at the late evolution time. The results of this study are of great significance for understanding cosmic evolution and solving cosmological problems.
Article
Astronomy & Astrophysics
Jose Ferreira, Tiago Barreiro, Jose Mimoso, Nelson J. Nunes
Summary: Using forthcoming ground and space based gravitational waves observatories, a Bayesian analysis was conducted to forecast constraints for a symmetric teleparallel gravity model with an ACDM background. The results suggest that ET is more effective in distinguishing this model from ACDM compared to LISA, and lower redshift events are favored for improving the quality of the constraints.
Article
Physics, Multidisciplinary
Tayyab Naseer, M. Sharif
Summary: In this paper, a non-static spherical geometry is considered and its extension for anisotropic matter configuration through minimal gravitational decoupling in f(R,T) theory is formulated. A particular transformation is applied to the radial metric function to divide the modified field equations into two distinct sectors corresponding to their parent sources. The unknowns in the isotropic set are reduced using the Friedmann-Lemaitre-Robertson-Walker cosmic model, and the isotropic solution is obtained using a linear equation of state and power-law form of the scale factor. The other set involves the decoupling function and components of an extra source, and a density-like constraint is adopted to close it. The role of this modified gravity and the decoupling parameter on three different eras of the cosmos is analyzed by graphically observing the developed extended solution, and it is concluded that the resulting solutions fulfill all the physical requirements only for the matter and radiation-dominated eras.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2023)
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, Multidisciplinary
S. Ghaffari, Giuseppe Gaetano Luciano, S. Capozziello
Summary: We constructed a holographic model for dark energy in the Brans-Dicke cosmology by incorporating the Barrow entropy. The Hubble horizon was used as the IR cutoff to explore the cosmological consequences. We found that both the non-interacting and interacting cases can explain the current accelerated expansion of the universe, unlike the standard holographic dark energy model. Stability analysis showed that the non-interacting model was unstable, while the sign-changeable interacting model was stable only for certain parameter values. The linear interacting model always predicted a stable universe. The consistency of the model with cosmological observations was discussed.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Mathematical
Salvatore Capozziello, Maurizio Capriolo, Gaetano Lambiase
Summary: The issue of defining gravitational energy in a given spatial region is still unresolved in General Relativity, except for particular cases of localized objects. In this study, we generalize the Einstein gravitational energy-momentum pseudotensor to non-local theories of gravity and consider analytic functions of the non-local integral operator ?(-1). By applying the Noether theorem to a gravitational Lagrangian invariant under infinitesimal rigid translations, we define a gravitational energy-momentum pseudotensor that transforms like a tensor under affine transformations. This pseudotensor, along with the energy-momentum complex, can be derived using the continuity equations considering gravitational and matter components, and their weak field limit is performed for astrophysical applications.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
S. Capozziello, S. Zare, D. F. Mota, H. Hassanabadi
Summary: In this study, the effects of a dark matter spike near the supermassive black hole in M87 (Virgo A galaxy) were investigated using the Bumblebee Gravity theory. The aim was to determine the impact of spontaneous Lorentz symmetry breaking on the horizon, ergo-region, and shadow of the Kerr Bumblebee black hole in the spike region. Dark matter distribution was incorporated into a Lorentz-violating spherically symmetric space-time, and the resulting solution was generalized to a Kerr Bumblebee black hole. The shapes of the shadow were examined based on observational data for the dark matter spike density and radius.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Salvatore Capozziello, Maria Caruana, Jackson Levi Said, Joseph Sultana
Summary: Teleparallel geometry provides a theoretical framework where gravitational interaction is mediated by torsion rather than curvature. Teleparallel analogue of Horndeski gravity is an approach within this framework considering scalar-tensor theories. It is a more general formalism than the standard metric one, allowing for a wider range of teleparallel Horndeski gravity models. The article explores constraints on these models in terms of ghost and Laplacian instabilities and finds that a large class of models is physically viable.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Editorial Material
Physics, Multidisciplinary
S. Capozziello, V. G. Gurzadyan
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Multidisciplinary
Stefano Camera, Salvatore Capozziello, Lorenzo Fatibene, Andrea Orizzonte
Summary: We investigate how the cosmological equation of state can be used to scrutinize extended theories of gravity, specifically the Palatini f(R) gravity. The effective equation of state produced by a given model is studied, and the inverse problem of determining which models are compatible with a given effective equation of state is also considered. We find that power-law models are capable of transforming barotropic Equations of State into effective barotropic ones, and the form of equation of state is preserved only for f(R) = R. Additionally, quadratic and non-homogeneous effective Equations of State contain the Starobinsky model and other models.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Marcello Miranda, Daniele Vernieri, Salvatore Capozziello, Valerio Faraoni
Summary: The physical nature of Horndeski gravity is explained as a dissipative effective fluid in a new approach. Requiring the constitutive equations of a Newtonian fluid restricts the theory to two subclasses of viable Horndeski gravity. A linear stress-energy tensor of the Horndeski effective fluid is sufficient for gravitational waves to propagate at light speed, while other Horndeski theories correspond to exotic non-Newtonian effective fluids. The two linear Horndeski classes are further studied in the framework of first-order thermodynamics of viscous fluids.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Multidisciplinary Sciences
Francesco Bajardi, Salvatore Capozziello, Tiziana Di Salvo, Francesca Spinnato
Summary: The Noether Symmetry Approach is a method for solving the dynamics of physical systems by selecting symmetries. It can be applied in various fields and is useful for selecting viable models and finding exact solutions.
Article
Astronomy & Astrophysics
Matteo Califano, Ivan de Martino, Daniele Vernieri, Salvatore Capozziello
Summary: We investigate four cosmological models that may solve the Hubble tension by considering different dark energy equation of state. By creating mock catalogs and extracting events associated with possible electromagnetic counterpart, we estimate the precision to which the Einstein Telescope can bound the cosmological parameters. Our results show that the uncertainty in the Hubble constant is always below 1%, potentially offering a solution to the Hubble tension. The accuracy on other cosmological parameters is comparable to current methods, except for the emergent dark energy model where the Einstein Telescope alone can significantly improve the limits.
Article
Astronomy & Astrophysics
Ester Piedipalumbo, Stefano Vignolo, Pasquale Feola, Salvatore Capozziello
Summary: In this study, we investigate the non-flat interacting quintessence cosmology within the framework of scalar-tensor gravity, where a scalar field interacts with dark matter. By employing the Noether Symmetry Approach, we obtain general exact solutions for cosmological equations and determine the scalar-field self-interaction potentials. The obtained solutions are capable of reproducing the accelerated expansion of the Universe and are consistent with various observational datasets, including the SNeIa Pantheon data, gamma ray bursts Hubble diagram, and direct measurements of the Hubble parameter.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
Vittorio De Falco, Francesco Bajardi, Rocco D'Agostino, Micol Benetti, Salvatore Capozziello
Summary: Various astrophysical methods are used to detect possible deviations from General Relativity in this work. A class of f(R) gravity models, selected by the existence of Noether symmetries, is considered. The study determines static and spherically symmetric black hole solutions that encompass small departures from the Schwarzschild geometry. The proposed strategy of using ray-tracing technique and considering the Poynting-Robertson effect proves to be robust and efficient in investigating gravity and detecting small deviations from General Relativity.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
G. G. L. Nashed, S. Capozziello
Summary: This study investigates the possible modifications of general relativity at ultraviolet and infrared scales, particularly considering the possibility of parity violation in strong gravity regime. The Chern-Simons gravity theory is used to account for the parity violation. The study shows that for certain spacetime structures, Chern-Simons gravity is equivalent to general relativity, but it is not applicable to (A)dS-Kerr/Kerr black holes. The thermodynamic quantities and geodesic equation of the black hole are also calculated.
Article
Astronomy & Astrophysics
M. G. Dainotti, A. L. Lenart, A. Chraya, G. Sarracino, S. Nagataki, N. Fraija, S. Capozziello, M. Bogdan
Summary: Currently, there is a debate about cosmological models and their corresponding parameters due to the discrepancy between H-0 obtained from SNe Ia and the Planck data. Considering high redshift probes like gamma-ray bursts (GRBs) is necessary but challenging due to the large range of GRB luminosities. In this study, we use the 3D Dainotti fundamental plane relation to infer cosmological parameters, and by considering selection and evolutionary effects, we obtain a lower intrinsic scatter compared to previous results. Our analysis, using GRB correlations and complemented with SNe Ia and BAO measurements, confirms the parameters of the Lambda cold dark matter model but with the advantage of using probes detected up to z = 5.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Physics, Particles & Fields
Salvatore Capozziello, Rocco D'Agostino, Alessio Lapponi, Orlando Luongo
Summary: We demonstrate the existence of black hole solutions that conform to the thermodynamics of logotropic fluids, which have recently been employed to address cosmological and astrophysical issues, within the framework of the Einstein field equations with a negative cosmological constant. This is accomplished by employing the generalization of logotropic fluids known as the Anton-Schmidt equation of state. We further investigate the construction of the anti-de Sitter metric, satisfying energy conditions, and explore alternative solutions by relaxing the strong energy condition.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Salvatore Capozziello, Rocco D'Agostino
Summary: This article explores non-local modifications of General Relativity by considering a distortion function in terms of the inverse of the d'Alembert operator. By using numerical methods and a model-independent approach based on current observations, the shape of the distortion function is reconstructed, and the best analytical approximation of the non-local Lagrangian is inferred. The results show that this non-local modification provides a natural explanation for late cosmic acceleration and avoids fine-tuning issues with the cosmological constant.
PHYSICS OF THE DARK UNIVERSE
(2023)
