Article
Astronomy & Astrophysics
Alexander Ganz
Summary: Minimally modified gravity models use auxiliary constraints to maintain a dynamic cosmological background, with results of linear perturbations being insensitive to constraint details, leading to a modified effective gravitational constant or a non-zero dust sound speed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
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
Astronomy & Astrophysics
Mohit Kumar Sharma, Sourav Sur
Summary: We analyze the dynamical system of interacting dark energy-matter scenarios and study the critical points and stability at both the background level and the level of density perturbations. We find a double degeneracy in the critical point spectrum in the inhomogeneous picture due to the possible growth and decay of matter density perturbations. By analyzing the dynamics of the growth factor, we show that it initially surpasses unity at one of the critical points and leads to a stable configuration as the matter density fluctuations diminish. As for the growth index, we find that the only physically plausible trajectory is one that evolves mildly at high redshifts and becomes steeper with time, with an average value close to 6/11.
PHYSICS OF THE DARK UNIVERSE
(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
Astronomy & Astrophysics
Celia Escamilla-Rivera, A. Hernandez-Almada, Miguel A. Garcia-Aspeitia, V Motta
Summary: This paper investigates a modified gravity Equation of State which can reproduce three cosmologically viable f(R) theories, and shows good agreement with the ΛCDM model and observational data sets, presenting a new method for analyzing the behavior of dynamical dark energy.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Astronomy & Astrophysics
Alvaro de la Cruz Dombriz, Francisco Jose Maldonado Torralba, David F. Mota
Summary: The stable pseudo-scalar degree of freedom in the quadratic Poincare Gauge theory of gravity is identified as a suitable candidate for dark matter. The study determines the parameter space in the theory that can explain all predicted cold dark matter phenomena and constrains these parameters with astrophysical observations.
Article
Physics, Particles & Fields
Jackie C. H. Liu
Summary: Based on the ratio gravity theory, we propose a mechanism to generate dynamical dark energy by coupling gravity with a quintessence field. This model leads to different behaviors of dark energy in the early and late universe, with the quintessence field starting as a constant and oscillating as the universe expands.
EUROPEAN PHYSICAL JOURNAL C
(2022)
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
Astronomy & Astrophysics
Weiqiang Yang, Eleonora Di Valentino, Supriya Pan, Yabo Wu, Jianbo Lu
Summary: This article compares various dynamical dark energy models using different observational data and discusses the alleviation of H-0 tension. Bayesian evidence analysis shows that all models perform better than Lambda CDM scenario, with the CPL model being the best in fitting the data and solving H-0 tension. However, the tension reappears when considering the baryon acoustic oscillations data, not supporting the dynamical dark energy solution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Miguel Aparicio Resco, Antonio L. Maroto
Summary: The study analyzes how to parametrize general modifications of the dark matter perturbations equations in a model-independent way, and shows that a general model with an imperfect and non-conserved dark matter fluid in a modified gravity scenario can be described with five general functions. It focuses on the sub-Hubble regime and finds that observable power spectra are sensitive to only three combinations of the initial five functions, which can help determine whether a modification of gravity or an imperfect/non-conserved dark matter is present. A Fisher forecast analysis for these three parameters is performed, with an example shown for a specific model with shear viscosity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Mohammad Ali Gorji, Hayato Motohashi, Shinji Mukohyama
Summary: In the context of scalar-tensor theories, stealth de Sitter solutions face issues of infinite strong coupling or gradient instability, which can be resolved by introducing a controlled detuning mechanism known as scordatura. This mechanism not only resolves the mentioned issues, but also ensures a well-defined quasi-static limit.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Marco Raveri, Levon Pogosian, Matteo Martinelli, Kazuya Koyama, Alessandra Silvestri, Gong -Bo Zhao
Summary: In this paper, a non-parametric reconstruction method is presented to determine three time-dependent functions in the cosmological model. The data constraints on the structure of these functions and their eigenmodes are analyzed. The results show that the combination of all data can constrain 15 combined eigenmodes of the three functions and explain the tensions between datasets.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Wenzhong Liu, Luis A. Anchordoqui, Eleonora Di Valentino, Supriya Pan, Yabo Wu, Weiqiang Yang
Summary: In recent cosmological observations, discrepancies have been found in the rate of expansion of the universe and the clustering of matter. A novel model proposes that cold dark matter disintegrates into dark radiation. However, this model fails to solve the discrepancy in the rate of expansion, although it can address the clustering issue under certain conditions. The effectiveness of these models is weakened when intermediate-redshift data is included.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Multidisciplinary Sciences
Shivangi Rathore, S. Surendra Singh
Summary: This paper investigates an interacting dark energy model in LRS Bianchi type I cosmological model with a scalar field in the form of an exponential potential. By calculating the critical points and eigenvalues of the Jacobian matrix, we find that the Universe is accelerating and obtain the critical points and behavior of dark energy for different coupling parameters.
SCIENTIFIC REPORTS
(2023)
Article
Astronomy & Astrophysics
Eleonora Di Valentino, Nils A. Nilsson, Mu-In Park
Summary: This study proposes a renormalizable, higher derivative, Lorentz-violating quantum gravity model without ghost problems known as Hoava gravity. Furthermore, a Hoava gravity-based dark energy (HDE) model is proposed by identifying the additional contributions from Lorentz-violating terms as an effective energy-momentum tensor in Einstein equation. The results show a preference for non-flat universes in the cosmic microwave background, baryon acoustic oscillation, and supernova Ia data tests, aligning with the cosmic concordance model.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)