Article
Physics, Particles & Fields
L. N. Granda
Summary: New corrections to General Relativity are proposed within the context of modified f(R) gravity that satisfy cosmological and local gravity constraints. The proposed models behave asymptotically as R - 2 Lambda at large curvature and show the vanishing of the cosmological constant at the flat spacetime limit. The steepness of the deviation parameter in late times leads to measurable signal of scalar tensor regime in matter perturbations, allowing departures from the ΛCDM model to be detected.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Astronomy & Astrophysics
Damianos Iosifidis
Summary: This passage introduces the foundation and characteristics of the Perfect (Ideal) Hyperfluid, including the microscopic features and energy tensors. It also discusses the conservation laws followed by this fluid structure, as well as its cosmological application and possible forms.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Pedro D. Alvarez, Benjamin Koch, Cristobal Laporte, Felipe Canales, Angel Rincon
Summary: We investigate the statefinder parameters in a cosmological model with scale-dependent gravity. The Einstein field equations are obtained from an average effective action. Analytical expressions are derived from the dynamical system to enhance the convergence of numerical solutions. We determine the statefinder parameters for moderate redshift and compare them with well-known alternatives to the ACDM model.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Tahere Kashfi, Mahmood Roshan
Summary: In this paper, a recently proposed relativistic theory for MOND is investigated using phase space analysis. The background cosmological equations of the theory are converted to a set of first-order autonomous equations. It is shown that the theory has a viable sequence of cosmological epochs and provides a richer structure in terms of the background cosmology.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Particles & Fields
Borna Salehian, Hong-Yi Zhang, Mustafa A. Amin, David Kaiser, Mohammad Hossein Namjoo
Summary: This paper systematically derives the SP equations and relativistic corrections from the nonlinear and fully relativistic KGE equations in an expanding universe, providing insights into deviations and applicability beyond the SP system. The method presented simplifies the analysis of scalar dark matter dynamics and accurately captures deviations from the SP system towards the full KGE case, particularly in calculating the mass-radius relationship of solitons.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Astronomy & Astrophysics
R. Maluf, Juliano C. S. Neves
Summary: In this work, a bumblebee field is utilized to generate cosmological anisotropies by violating Lorentz symmetry through a nonzero vacuum expectation value. When coupled to Bianchi I geometry, the bumblebee field produces a preferred axis, contributing to cosmic anisotropies. The article concludes by attempting to place an upper limit on the bumblebee field using the quadrupole and octopole moments of the cosmic microwave background radiation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Damianos Iosifidis, Konstantinos Pallikaris
Summary: In this work, we introduce metric-affine theories in a new way by changing the field variables. We present a set of equivalent frameworks and provide detailed identifications. The advantage of using these new frameworks is that any metric-affine theory can be treated as a Riemannian theory with additional fields. We investigate the Hilbert-Palatini action and reveal interesting symmetries under SO transformations in field space. Then, we use solvable Riemannian theories as seed models for solvable metric-affine theories, focusing on three examples. We present a black hole solution with torsion and non-metricity that becomes regular under certain tuning. Additionally, we report a de Sitter universe with expansion powered by 3-form torsion.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Nuclear
Mihai Marciu, Dana Maria Ioan
Summary: This paper extends the basic Einstein-Hilbert action by introducing a non-minimal coupling between the space-time geometry and matter fields. It formulates a cosmological model based on specific associations between the matter energy-momentum tensor and the Einstein tensor. The dynamics of the model and its physical implications are explored through a dynamical system analysis.
Article
Astronomy & Astrophysics
I. E. C. R. Mendonca, Kamal Bora, R. F. L. Holanda, Shantanu Desai
Summary: In this study, possible cosmological signatures were searched for using galaxy cluster gas mass fraction measurements and cosmic chronometers. The results show that no significant departure from general relativity was found regardless of assumptions about cosmic curvature or a possible depletion factor evolution in cluster measurements.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Kieran Wood, Paul M. Saffin, Anastasios Avgoustidis
Summary: Expanding the clockwork mechanism to gravitational interactions allows for the generation of exponentially suppressed coupling to matter, without the need for large hierarchies or a dilaton. By constructing appropriate potentials, the theory exhibits the desired clockwork effect. Additionally, cosmological solutions within this framework are considered, revealing the existence of multiple deSitter vacua. Furthermore, the continuum limit of the theory is clarified, demonstrating its applicability to cosmological solutions in ghost free multi-gravity theories with nearest-neighbour interactions.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Particles & Fields
Amara Ilyas, Mian Zhu, Yunlong Zheng, Yi-Fu Cai
Summary: This article presents an emergent universe scenario derived from DHOST cosmology. The universe transitions from an asymptotic Minkowski state in the far past to a radiation dominated period in the late stage, providing a graceful exit. Analysis shows that cosmological perturbations are stable, and the primordial scalar spectrum is discussed for achieving scale invariance.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Astronomy & Astrophysics
Kieran Wood, Paul M. Saffin, Anastasios Avgoustidis
Summary: This article introduces the higher order generalisation of the clockwork mechanism for gravitational interactions and its potential application, and discusses the formation of the clockwork effect and the construction of cosmological solutions in multi-gravity theories. The study shows that the evolution of the metric in the theory is essentially equivalent to that of general relativity at the modified Planck scale, and it has the potential to address cosmological issues. Additionally, the article clarifies the properties of the theory in the continuum limit.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Particles & Fields
Wei Cheng, Yuan He, Jing-Wang Diao, Yu Pan, Jun Zeng, Jia-Wei Zhang
Summary: This paper investigates the testing of WIMP dark matter models by introducing an interaction term between dark energy and WIMP dark matter. The study reveals new insights on the evolution of parameters associated with dark matter freeze-out temperature and the magnification of dark matter relic density. The results suggest that with more precise cosmological observations, more stringent constraints can be placed on the WIMP dark matter models.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Polina Petriakova, Arkady A. Popov, Sergey G. Rubin
Summary: This paper discusses the origin of small parameters and aims to explain the Hierarchy problem. Flexible extra dimensions play a crucial role in the formation of physical parameters. The evolution of multidimensional metric starts from the Planck scale and ends with a static extra-dimensional metric and a 4-dimensional de Sitter space at high energies, leading to exponentially produced causally disconnected universes. Quantum fluctuations independently distort the metric within these universes, causing inflationary processes. Some universes asymptotically tend towards states characterized by small Hubble parameters. The explanation for the effective parameter reduction in the Higgs sector of the Standard Model lies in the presence of small-amplitude distributions of a scalar field in a fraction of these universes.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Yunlong Zheng
Summary: Two types of mimetic gravity models with higher derivatives of the mimetic field are analyzed in the Hamiltonian formalism. The number of degrees of freedom (DOFs) is different between the two models. In the unitary gauge, the Dirac matrix becomes singular, resulting in extra constraints and reducing the number of DOFs.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)