Article
Physics, Multidisciplinary
Ahmad Sheykhi, Maral Sahebi Hamedan
Summary: The thermodynamics-gravity conjecture suggests a strong connection between the gravitational field equations and the first law of thermodynamics, meaning any changes in entropy expression directly impact the field equations. By considering the modified Barrow entropy associated with the apparent horizon, the Friedmann equations are altered as well. This paper explores the implications of this modification on the holographic dark energy (HDE) model, highlighting changes in energy density and the Friedmann equations. The study also investigates the cosmological consequences of using the Hubble horizon and future event horizon as infrared cutoffs, including interactions between dark matter (DM) and dark energy (DE), and the impact of the Barrow exponent on the cosmological behavior of HDE, such as crossing the phantom line and shifting the universe phase transition time.
Article
Astronomy & Astrophysics
Yuewei Wen, Eva Nesbit, Dragan Huterer, Scott Watson
Summary: Standard cosmological data analyses can't easily determine the presence of modified gravity. This study presents a quantitative mapping showing how modified gravity models appear within standard analyses, reporting specific biases in standard-parameter spaces. The implications for measurements of mass fluctuations are also discussed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Antonio De Felice, Shinji Mukohyama
Summary: This paper introduces a new cosmological framework integrating dark matter into a minimally modified gravity model, maintaining the same number of gravitational degrees of freedom through a series of transformations. The framework includes two time-dependent free functions to achieve desired evolutions of Hubble expansion rate and effective gravitational constant for dark matter.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Particles & Fields
Armin van de Venn, David Vasak, Johannes Kirsch, Juergen Struckmeier
Summary: The paper investigates the implications of metric compatible covariant canonical gauge theory of gravity on cosmological scales. The resulting equations of motion in a Friedmann-Lemaitre-Robertson-Walker Universe are derived for a totally anti-symmetric torsion tensor. The modifications of the Friedmann equations, equivalent to spatial curvature, are shown in the limit of a vanishing quadratic Riemann-Cartan term and are further investigated in the early and late times of the Universe's history.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Artyom V. Astashenok, Sergey D. Odintsov, Vasilis K. Oikonomou
Summary: In this paper, we investigate realistic models of compact objects, focusing on neutron and strange stars composed of dense matter and dark energy. We consider different scenarios for dark energy, including simple fluid or scalar field interacting with matter, modified gravity combined with dark energy, and dark energy as scalar field non-minimally interacting with gravity.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Mathematical
Artyom Astashenok, Alexander S. Tepliakov
Summary: This paper investigates the Tsallis holographic dark energy model in the framework of Nojiri-Odintsov gravity. The results show that this model can describe observational data and has an oscillating Hubble parameter in the future. Additionally, the study reveals that the occurrence of singularities is associated with the zero second derivative of f(R).
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
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
Astronomy & Astrophysics
Gary Nash
Summary: MGR is the natural extension of GR, which uses a smooth regular line element vector field (X,-X) to construct a connection-independent symmetric tensor representing the energy-momentum of the gravitational field. It solves the localization problem of gravitational energy-momentum in GR and maintains the equivalence principle. The line element field provides MGR with the extra freedom to describe dark energy and dark matter.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Physics, Multidisciplinary
M. Zubair, Lala Rukh Durrani, Saira Waheed
Summary: In this paper, a reconstruction of the f(T, B) gravity model is conducted, showing that all reconstructed models favor the current accelerated expansion regime by representing phantom cosmic epoch or de-Sitter model for different scenarios. The validity of the null energy condition is only observed for one case, while it remains invalid for other cases. Additionally, the stability of the reconstructed models is explored, revealing that both power law and de-Sitter solutions exhibit stable behavior against introduced perturbations.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Physics, Mathematical
Abdul Jawad, Sabir Hussain
Summary: This paper investigates the Tsallis holographic dark energy model in different cosmological contexts, analyzing various cosmological parameters and planes, and comparing them with the Planck data to draw conclusions about the consistency of cosmic expansion.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2021)
Article
Astronomy & Astrophysics
Chunshan Lin
Summary: This study presents a general covariant local field theory of the holographic dark energy model, showing that the low energy effective theory is the massive gravity theory with a scalar graviton having strong coupling at certain energy scale. The UV-IR correspondence in this model stems from the breakdown of the effective field theory at the energy scale.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Multidisciplinary
Peiran Yin, Rui Li, Chengjiang Yin, Xiangyu Xu, Xiang Bian, Han Xie, Chang-Kui Duan, Pu Huang, Jian-hua He, Jiangfeng Du
Summary: In this study, the chameleon theory as a candidate explanation for dark energy is ruled out by experimental tests, providing decisive conclusions and demonstrating the reliability of laboratory experiments for uncovering the nature of dark energy in the future.
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
Multidisciplinary Sciences
Cosmin Andrei, Anna Ijjas, Paul J. Steinhardt
Summary: In this paper, we investigate how short the remaining period of expansion can be given current observational constraints on dark energy, and discuss how this scenario fits naturally with cyclic cosmologies and recent conjectures about quantum gravity.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
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
Astronomy & Astrophysics
Lorenzo Iorio
Summary: The potential habitability of putative natural massive satellites orbiting Jupiter-like planets has gained attention. Long-term variations in the satellite's obliquity under different initial spin-orbit configurations were identified. Factors like tidal dissipations were not included in the present analysis, indicating a need for further research.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Lorenzo Iorio
Summary: This article discusses the potential application of the mean anomaly at epoch eta in gravitational tests, as well as the reasons why astronomers have not used this parameter so far.
Article
Astronomy & Astrophysics
Lorenzo Iorio
Summary: This study investigates the measurable characteristic time-scales of transiting exoplanets and examines if the cumulative shifts induced by the post-Newtonian gravitoelectric and gravitomagnetic components of the stellar gravitational field are measurable. Analytical calculations are performed for different time intervals associated with primary and secondary transits of a fictitious Sun-Jupiter system, and the results are compared with experimental accuracies for HD 286123 b exoplanet. The study suggests that the pN gravitoelectric shift may become measurable at a certain level of relative accuracy after continuous monitoring for a certain duration.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Lorenzo Iorio, Matteo Luca Ruggiero
Summary: This study analytically calculates the effect of modified gravity models on the radial velocity of binary systems and specifically calculates the impact of the cosmological constant. The results show that the influence of the cosmological constant on the radial velocity of the Proxima/alpha Centauri AB binary system can be considered negligible.
Article
Astronomy & Astrophysics
Lorenzo Iorio
Summary: Extrasolar circumbinary planets are planets that orbit two stars instead of one. Research has found that when the orbital frequency of the stellar pair is higher than that of the planet, the tight stellar binary can generate its own gravitomagnetic field, affecting the orbital motion of a distant planet. The Lense-Thirring precessional effects can be significant, depending on the masses of the system's bodies.
Correction
Astronomy & Astrophysics
L. Iorio
ASTRONOMICAL JOURNAL
(2023)
Correction
Astronomy & Astrophysics
Lorenzo Iorio
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Astronomy & Astrophysics
Lorenzo Iorio
Summary: With the second post-Newtonian (2PN) calculations using the Gauss perturbing equations and the osculating Keplerian orbital elements, the Hermean average perihelion rate ranges from -18 to -4 microarcseconds per century, depending on the true anomaly. It is influenced by both direct and indirect effects of the Sun's gravitational field. The experimental measurement of Mercury's perihelion rate has an uncertainty of 8 microarcseconds per century, but the realistic uncertainty may be much larger.
Article
Astronomy & Astrophysics
Lorenzo Iorio, Athul Pradeepkumar Girija, Daniele Durante
Summary: In recent years, there has been a growing interest in sending a mission to Uranus, which has only been visited by Voyager 2 in 1986. The Elliptical Uranian Relativity Orbiter is investigating the possibility of measuring the planet's angular momentum by studying the Lense-Thirring effect on a potential orbiter. By choosing an appropriate orbital configuration, it is possible to separate the relativistic precessions from the classical rates induced by the planet's gravity field. The uncertainties in the orientation of the planetary spin axis and the inclination are the main sources of systematic bias and need to be determined accurately.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Lorenzo Iorio
Summary: The new geodetic satellite LARES 2, launched last year, aims to measure the Lense-Thirring node precessions independently using the sum of the nodes of LAGEOS and LARES 2. However, the current uncertainties in the orbital configurations of both satellites and the imperfect knowledge of the Earth's angular momentum make it challenging to achieve the desired accuracy goal. It is suggested that modeling and simultaneously estimating dedicated parameters, along with other characteristics of the geopotential, would be a breakthrough in reliably testing the gravitomagnetic field of the Earth.
Article
Physics, Multidisciplinary
Matteo Luca Ruggiero
Summary: In this study, the authors utilize Fermi coordinates to analyze the interaction between a plane gravitational wave and a proper detector frame. They emphasize the analogy between the effects of the gravitational wave and the electromagnetic field, particularly in terms of a Lorentz-like force equation. The authors focus on the impact of the wave on time measurements and evaluate its magnitude. Additionally, they calculate the expression of the local spacetime metric in cylindrical coordinates and explore its relevance to the helicity-rotation coupling.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Lorenzo Iorio
Summary: The preliminary investigation focuses on detecting the gravitomagnetic Lense-Thirring effect on the orbits of Jupiter's Galilean moons caused by their angular momentum. Numerical integrations suggest that the expected signatures of the effect on the satellites' observable positions can reach tens of arcseconds for Io, but drop to a level of around 0.2 arcseconds for Callisto. While modeling errors in the Jovian gravity field and Jupiter's spin axis may have some impact, future improvements in determining these parameters are expected. Accurate knowledge of the satellites' masses is crucial and can be achieved through future missions to the Jovian system. Present-day accuracy in determining the orbits of the Galilean satellites is around 10 milliarcseconds, but ongoing efforts to re-reduce old photographic plates may further improve this accuracy, making it possible to detect the Lense-Thirring effect in the future with dedicated data reductions.
Article
Astronomy & Astrophysics
Davide Astesiano, Matteo Luca Ruggiero
Summary: In this study, the gravitoelectromagnetic approach is used to investigate the impact of general relativity on galactic dynamics under the weak-field and slow-motion approximation. Contrary to expectations, a specific class of solutions for the gravitomagnetic field is shown to introduce non-negligible corrections to the Newtonian velocity profile. The origin and interpretation of these corrections are discussed, and explicit applications to various galactic models are provided.
Correction
Astronomy & Astrophysics
L. Iorio
Article
Astronomy & Astrophysics
Davide Astesiano, Matteo Luca Ruggiero
Summary: This study explores disk galaxies within the framework of general relativity, investigating the potential corrections to the purely Newtonian approach even in the low energy limit. By considering both low energy expansion and exact solutions, the connection between these different approaches is clarified. The analysis focuses on two different limits - gravitomagnetic analogy and strong gravitomagnetism - which show corrections of the same order as the Newtonian terms. The findings suggest a geometrical origin for a certain amount of dark matter effects, explaining the observed flat velocity profile without the need for dark matter contributions.
