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13 pages, 359 KB

Open AccessArticle

Toward the Alleviation of the H₀ Tension in Myrzakulov f(R,T) Gravity

by Mashael A. Aljohani, Emad E. Mahmoud, Koblandy Yerzhanov and Almira Sergazina

Universe 2025, 11(8), 252; https://doi.org/10.3390/universe11080252 - 29 Jul 2025

Cited by 1 | Viewed by 419

In this work, we provide a promising way to alleviate the Hubble tension within the framework of Myrzakulov

f (R, T)

gravity. The latter incorporates both curvature and torsion under a non-special connection. We consider the [...] Read more.

In this work, we provide a promising way to alleviate the Hubble tension within the framework of Myrzakulov

f (R, T)

gravity. The latter incorporates both curvature and torsion under a non-special connection. We consider the

f (R, T) = R + α R^{2}

class, which leads to modified Friedmann equations and an effective dark energy sector. Within this class, we make specific connection choices in order to obtain a Hubble function that coincides with that of

Λ

CDM at early times while yielding higher

H_{0}

values at late times. The reason behind this behavior is that the dark energy equation of state exhibits phantom behavior, which is known to be a sufficient mechanism for alleviating the

H_{0}

tension. A full observational comparison with various datasets, including the Cosmic Microwave Background (CMB), is required to test the viability of this scenario. Strictly speaking, the present work does not provide a complete solution to the Hubble tension but rather proposes a promising way to alleviate it. Full article

(This article belongs to the Special Issue Gravity and Cosmology: Exploring the Mysteries of f(T) Gravity)

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15 pages, 1931 KB

Open AccessArticle

Observational Constraints and Cosmographic Analysis of f(T,T_G) Gravity and Cosmology

by Harshna Balhara, Jainendra Kumar Singh, Shaily and Emmanuel N. Saridakis

Symmetry 2024, 16(10), 1299; https://doi.org/10.3390/sym16101299 - 2 Oct 2024

Cited by 12 | Viewed by 2889

Abstract

We perform observational confrontation and cosmographic analysis of

f (T, T_{G})

We perform observational confrontation and cosmographic analysis of

f (T, T_{G})

gravity and cosmology. This higher-order torsional gravity is based on both the torsion scalar, as well as on the teleparallel equivalent of the Gauss–Bonnet combination, and gives rise to an effective dark-energy sector which depends on the extra torsion contributions. We employ observational data from the Hubble function and supernova Type Ia Pantheon datasets, applying a Markov chain Monte Carlo sampling technique, and we provide the iso-likelihood contours, as well as the best-fit values for the parameters of the power-law model, an ansatz which is expected to be a good approximation of most realistic deviations from general relativity. Additionally, we reconstruct the effective dark-energy equation-of-state parameter, which exhibits a quintessence-like behavior, while in the future the Universe enters into the phantom regime, before it tends asymptotically to the cosmological constant value. Furthermore, we perform a detailed cosmographic analysis, examining the deceleration, jerk, snap, and lerk parameters, showing that the transition to acceleration occurs in the redshift range

0.52 \leq z_{t r} \leq 0.89

, as well as the preference of the scenario for quintessence-like behavior. Finally, we apply the Om diagnostic analysis to cross-verify the behavior of the obtained model. Full article

(This article belongs to the Special Issue Symmetry in Cosmological Theories and Observations)

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7 pages, 269 KB

Open AccessArticle

Cartan F(R) Gravity and Equivalent Scalar–Tensor Theory

by Tomohiro Inagaki and Masahiko Taniguchi

Symmetry 2022, 14(9), 1830; https://doi.org/10.3390/sym14091830 - 3 Sep 2022

Cited by 7 | Viewed by 1795

Abstract

We investigate the Cartan formalism in

F (R)

gravity.

F (R)

gravity has been introduced as a theory to explain cosmologically accelerated expansions by replacing the Ricci scalar R in the Einstein–Hilbert action with a function of R. [...] Read more.

We investigate the Cartan formalism in

F (R)

gravity.

F (R)

gravity has been introduced as a theory to explain cosmologically accelerated expansions by replacing the Ricci scalar R in the Einstein–Hilbert action with a function of R. As is well-known,

F (R)

gravity is rewritten as a scalar–tensor theory by using the conformal transformation. Cartan

F (R)

gravity is described based on the Riemann–Cartan geometry formulated by the vierbein-associated local Lorenz symmetry. In the Cartan formalism, the Ricci scalar R is divided into two parts: one derived from the Levi–Civita connection and the other from the torsion. Assuming the spin connection-independent matter action, we have successfully rewritten the action of Cartan

F (R)

gravity into the Einstein–Hilbert action and a scalar field with canonical kinetic and potential terms without any conformal transformations. red Thus, symmetries in Cartan

F (R)

gravity are clearly conserved. The resulting scalar–tensor theory is useful in applications of the usual slow-roll scenario. As a simple case, we employ the Starobinsky model and evaluate fluctuations in cosmological microwave background radiation. Full article

(This article belongs to the Special Issue Symmetry with Gravity and Particle Theories)

18 pages, 362 KB

Open AccessEditor’s ChoiceArticle

Minisuperspace Quantum Cosmology in Metric and Affine Theories of Gravity

by Salvatore Capozziello and Francesco Bajardi

Universe 2022, 8(3), 177; https://doi.org/10.3390/universe8030177 - 10 Mar 2022

Cited by 13 | Viewed by 3186

Abstract

Minisuperspace Quantum Cosmology is an approach by which it is possible to infer initial conditions for dynamical systems which can suitably represent observable and non-observable universes. Here we discuss theories of gravity which, from various points of view, extend Einstein’s General Relativity. Specifically, [...] Read more.

f (R)

f (T)

, and

f (G)

gravity, with R, T, and

G

being the curvature, torsion and Gauss–Bonnet scalars, respectively, is developed starting from the Arnowitt–Deser–Misner approach. The Minisuperspace Quantum Cosmology is derived for all these models and cosmological solutions are obtained thanks to the existence of Noether symmetries. The Hartle criterion allows the interpretation of solutions in view of observable universes. Full article

(This article belongs to the Special Issue Quantum Cosmology)

12 pages, 312 KB

Open AccessArticle

Metric-Affine Version of Myrzakulov F(R,T,Q,

T

) Gravity and Cosmological Applications

by Damianos Iosifidis, Nurgissa Myrzakulov and Ratbay Myrzakulov

Universe 2021, 7(8), 262; https://doi.org/10.3390/universe7080262 - 23 Jul 2021

Cited by 27 | Viewed by 2890

Abstract

We derive the full set of field equations for the metric-affine version of the Myrzakulov gravity model and also extend this family of theories to a broader one. More specifically, we consider theories whose gravitational Lagrangian is given by [...] Read more.

F (R, T, Q, T, D)

where T, Q are the torsion and non-metricity scalars,

T

is the trace of the energy-momentum tensor and

D

the divergence of the dilation current. We then consider the linear case of the aforementioned theory and, assuming a cosmological setup, we obtain the modified Friedmann equations. In addition, focusing on the vanishing non-metricity sector and considering matter coupled to torsion, we obtain the complete set of equations describing the cosmological behavior of this model along with solutions. Full article

(This article belongs to the Special Issue Modified Theories of Gravity and Cosmological Applications)

24 pages, 406 KB

Open AccessReview

Some Mathematical Aspects of f(R)-Gravity with Torsion: Cauchy Problem and Junction Conditions

by Stefano Vignolo

Universe 2019, 5(12), 224; https://doi.org/10.3390/universe5120224 - 6 Dec 2019

Cited by 5 | Viewed by 2938

Abstract

We discuss the Cauchy problem and the junction conditions within the framework of

f (R)

-gravity with torsion. We derive sufficient conditions to ensure the well-posedness of the initial value problem, as well as general conditions to join together on a [...] Read more.

We discuss the Cauchy problem and the junction conditions within the framework of

f (R)

-gravity with torsion. We derive sufficient conditions to ensure the well-posedness of the initial value problem, as well as general conditions to join together on a given hypersurface two different solutions of the field equations. The stated results can be useful to distinguish viable from nonviable

f (R)

-models with torsion. Full article

(This article belongs to the Special Issue Torsion-Gravity and Spinors in Fundamental Theoretical Physics)

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