Article
Astronomy & Astrophysics
Andrius Tamosiunas, Chad Briddon, Clare Burrage, Alan Cutforth, Adam Moss, Thomas Vincent
Summary: A key goal in cosmology is to better understand the accelerated expansion of the Universe. This study focuses on the chameleon screening phenomenon in cosmic voids and uses analytical and numerical methods to investigate its impact on structure formation. The results show a complex relationship between the properties of cosmic voids and the chameleon acceleration of test particles. The study also discusses the optimal density profiles for detecting the fifth force in upcoming observational surveys.
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
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
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
Sergei F. Shandarin
Summary: The study examines the density distribution of dark matter at caustic surfaces and the corresponding geometrical features, as well as the methods and challenges in identifying caustics in numerical simulations. The halo boundary is found to be asymmetrical, but a convex hull is a good approximation. Analyses of kinetic and potential energies, as well as examination of the two-dimensional phase space, confirm that the halo is gravitationally bound. The discovery of non-ellipsoidal oval shapes in a sample of halos from large simulations shows promise for further detailed analysis on higher resolution simulations.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Eric J. Baxter, Jason Kumar, Aleczander D. Paul, Jack Runburg
Summary: This article investigates the gamma-ray signals of dark matter annihilation in extragalactic halos, focusing on the cases where dark matter annihilates from a p-wave or d-wave state. The study finds that by analyzing the gamma rays produced by dark matter annihilation in halos detected by the Sloan Digital Sky Survey, evidence for dark matter annihilation can be found, although distinguishing between the p-wave and d-wave scenarios remains challenging. However, with a higher exposure, discrimination of the velocity-dependence becomes possible.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
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
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
Ehsan Ebrahimian, Aliakbar Abolhasani
Summary: We investigate the alignment of spin and speed in dark matter halos using tidal-locking theory (TLT) and find partial alignment for large high-speed halos. We also compare the results to tidal torque theory (TTT) and find different alignment effects at different redshifts.
ASTROPHYSICAL JOURNAL
(2022)
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
Abdolali Banihashemi, Nima Khosravi, Arman Shafieloo
Summary: A new critically emergent dark energy model (CEDE) is proposed, which is consistent with both Planck's CMB data and Riess et al.'s local Hubble constant measurements. The model suggests that dark energy emerges at a transition redshift, providing a possible explanation for the Hubble constant tension.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(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
Astronomy & Astrophysics
Andreas Lymperis
Summary: By investigating the features of a non-metricity scalar Q function, the cosmological implications of f(Q) gravity are explored, and analytical expressions for the dark energy density, equation-of-state, and deceleration parameters are obtained. The study reveals that even in the absence of a cosmological constant, the universe follows the usual thermal history with matter and dark energy eras, and the dark energy equation-of-state parameter remains in the phantom regime. Additionally, the scenario shows excellent agreement with observational data from Supernovae type Ia. Furthermore, it is demonstrated that f(Q) gravity can effectively mimic the behavior of a cosmological constant.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Abdul Jawad, Zain ul Abideen, Shamaila Rani
Summary: In this paper, the cosmic analysis of the Kaniadakis holographic dark energy model is investigated in the frameworks of f(G) and f(similar to)(T) modified theories of gravity. The functional forms of f(G) and f(similar to)(T) models are reconstructed using a power-law form of scale factor and flat FRW metric. The behavior of these functional forms with respect to their arguments is discussed. Various cosmic parameters are explored using these models to discuss the accelerated expansion of the universe, and consistent results are obtained for specific values of model parameters.
MODERN PHYSICS LETTERS A
(2023)
Article
Astronomy & Astrophysics
Hayley J. Macpherson
Summary: In this study, a new ray-tracing tool is introduced to calculate cosmological distances in the context of fully nonlinear general relativity. The ability of the general cosmographic representation of luminosity distance, truncated at third order in redshift, to accurately capture anisotropies is investigated. It is found that the third-order cosmography is accurate to within 1% for redshifts up to approximately 0.034, but the inclusion of small-scale structure compromises its accuracy.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)