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Astronomy & Astrophysics
M. Senay
Summary: This paper investigates the effects of fermionic q deformation on Einstein's field equations and Friedmann equations by representing the thermodynamical properties of the deformed fermion gas model and deriving deformed Einstein field equations and Friedmann equations. The behavior of quantum black holes is described, and effective values for the energy density, pressure, and equation of state for dark energy are presented. Finally, an analytical expression for the effective density parameter of dark energy is derived.
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
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
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
Matteo Lucca
Summary: In the effort to address the Hubble tension, it is necessary to consider models that can modify the expansion and thermal history of the Universe, while maintaining overall concordance between early and late-time observations. A multi-interacting dark energy model with two complementary interaction channels has been explored, showing potential in resolving the S-8 tension but ultimately unable to restore the overall concordance between early and late-time observations.
Article
Astronomy & Astrophysics
Jiwon Park, Tae Hoon Lee
Summary: In this paper, the authors propose an f(R) gravity model to explain dark energy which can also be applied to a type of galactic dark matter. By constructing f(R) gravitational Lagrangians through a Legendre transform from scalar-tensor theories, the future behavior of the late-time accelerating Universe as well as the subsequent behavior of an inflation model are studied. Moreover, possible relations to galactic dark matter are discussed, with a spherically symmetric solution obtained for the static metric in the f(R) model.
MODERN PHYSICS LETTERS A
(2023)
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
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
Yogendra Srivastava, Giorgio Immirzi, John Swain, Orlando Panella, Simone Pacetti
Summary: This article discusses a general class of axially symmetric metrics in general relativity that includes rotations, which are used to study the dynamics of rotationally supported galaxies. The exact vacuum solutions of the Einstein equations for this extended Weyl class of metrics lead to the following rigorous deductions: (i) The rotational velocity in general relativity always exceeds the Newtonian velocity due to Lenz's law. (ii) A non-zero intrinsic angular momentum for a galaxy requires the asymptotic constancy of the Weyl length parameter, similar to the Kerr metric. (iii) The asymptotic constancy of the parameter also implies a plateau in the rotational velocity. Unlike the Kerr metric, the extended Weyl metric can be extended within the galaxy, and it has been shown that Gauss and Ampere laws emerge along with Ludwig's extended gravito-electromagnetism (GEM) theory and non-linear rate equations for the velocity field. More accurate estimates for the Sun's escape velocity than those obtained from Newtonian theory have been presented.
EUROPEAN PHYSICAL JOURNAL C
(2023)
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
Xavier Calmet, Nathaniel Sherrill
Summary: This paper demonstrates that atom interferometer experiments, such as MAGIS, AION, and AEDGE, have the potential to probe both very light dark matter models and quantum gravity. The linear coupling between a singlet scalar dark matter particle and electrons or photons is ruled out by current understanding of quantum gravity and torsion pendulum experiments. However, the quadratic coupling of scalar dark matter with electrons and photons has a large viable parameter space that can be explored by these atom interferometers. The implications for quantum gravity searches are discussed.
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
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)
Review
Astronomy & Astrophysics
Veronica Motta, Miguel A. Garcia-Aspeitia, Alberto Hernandez-Almada, Juan Magana, Tomas Verdugo
Summary: The article summarizes the characteristics of dark energy models and some commonly used cosmological samples, discusses how to constrain model parameters using observational data, and finally provides an overview of the status of dark energy modeling.
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Astronomy & Astrophysics
Rafaela Gsponer, Johannes Noller
Summary: This study discusses and derives criteria for the presence and size of tachyonic instabilities in dark energy theories. The findings suggest that tachyonic instabilities do not significantly affect the cosmological validity of the models, unlike ghost and gradient instabilities.
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Astronomy & Astrophysics
Sanved Kolekar, T. Padmanabhan
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T. Padmanabhan
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T. Padmanabhan
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Krishnamohan Parattu, Sumanta Chakraborty, T. Padmanabhan
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Astronomy & Astrophysics
T. Padmanabhan, Sumanta Chakraborty, Dawood Kothawala
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(2016)
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Astronomy & Astrophysics
Krishnamohan Parattu, Sumanta Chakraborty, Bibhas Ranjan Majhi, T. Padmanabhan
GENERAL RELATIVITY AND GRAVITATION
(2016)
Review
Astronomy & Astrophysics
T. Padmanabhan
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2016)
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Physics, Multidisciplinary
Kinjalk Lochan, T. Padmanabhan
PHYSICAL REVIEW LETTERS
(2016)
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Astronomy & Astrophysics
Sumanta Chakraborty, Sourav Bhattacharya, T. Padmanabhan
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Astronomy & Astrophysics
Kinjalk Lochan, Krishnamohan Parattu, T. Padmanabhan
GENERAL RELATIVITY AND GRAVITATION
(2015)
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Astronomy & Astrophysics
Thanu Padmanabhan
COMPTES RENDUS PHYSIQUE
(2017)
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Astronomy & Astrophysics
Kinjalk Lochan, Sumanta Chakraborty, T. Padmanabhan
Proceedings Paper
Mechanics
Thanu Padmanabhan
EMQM15: EMERGENT QUANTUM MECHANICS 2015
(2016)
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Multidisciplinary Sciences
T. Padmanabhan