326 citations · 1.5k across the 52 of their papers we have counts for
52 papers
New generalization of the Barboza-Alcaniz parametrization of Dark energy
Shahab Shahidi
A generalization of the Barboza-Alcaniz parametrization of dark energy is proposed. This is a three-parameter model which can resolve the shortcomings of the Barboza-Alcaniz behavi…
Dark energy and accelerating cosmological evolution in a Universe with a Weylian boundary
Tiberiu Harko, Shahab Shahidi
We investigate the influence of boundary terms in gravitational field theories, by considering that in the Einstein-Hilbert action the boundary can be described by a non-metric Wey…
Dark energy and a new realization of the matter Lagrangian
Shahab Shahidi, Sedigheh Farahzad
A new realization of the matter Lagrangian is introduced which models the dark energy component as a non-standard combination of thermodynamics quantities of the baryonic matter. W…
Cosmology in generalized hybrid metric-Palatini with matter-geometry coupling
Reza Jalali, Shahab Shahidi, Mohammad Hossein Zhoolideh Haghighi
Cosmological implications of a class of hybrid metric-Palatini gravity with a non-minimal matter-geometry coupling is considered. The theory contains a metric curvature tensor, tog…
Cosmological implications of hybrid metric-Palatini gravity
Shahab Shahidi, Shiva Kayedi
The hybrid metric-Palatini gravity with Lagrangian density is considered, where is the metric Ricci scalar and $\mathcal{…
From Barthel Randers Kropina Geometries to the Accelerating Universe: A Brief Review of Recent Advances in Finslerian Cosmology
Amine Bouali, Himanshu Chaudhary, Lehel Csillag +4
We review recent developments in cosmological models based on Finsler geometry and extensions of general relativity within this framework. Finsler geometry generalizes Riemannian g…
Mimetic Weyl geometric gravity
Daria-Ioana Visa, Tiberiu Harko, Shahab Shahidi
We consider a mimetic type extension of the Weyl geometric gravity theory, by assuming that the metric of the space-time manifold can be parameterized in terms of a scalar field, c…
Cosmological implications of the Weyl geometric gravity theory
Tiberiu Harko, Shahab Shahidi
We consider cosmological implications of the Weyl geometric gravity theory. The basic action of the model is obtained from the simplest conformally invariant gravitational action,…
Reply to Comment on "Dark matter as a Weyl geometric effect"
Piyabut Burikham, Tiberiu Harko, Kulapant Pimsamarn +1
In a recent Comment on the paper "Dark matter as a Weyl geometric effect", by Burikham et al., Phys. Rev. D 107, 064008 (2023), posted on arxiv. org as eprint arXiv:2306.11926, it…
Dark matter as a Weyl geometric effect
Piyabut Burikham, Tiberiu Harko, Kulapant Pimsamarn +1
We investigate the possibility that the observed behavior of test particles outside galaxies, which is usually explained by assuming the existence of dark matter, is the result of…
The first variation of the matter energy-momentum tensor with respect to the metric, and its implications on modified gravity theories
Zahra Haghani, Tiberiu Harko, Shahab Shahidi
The first order variation of the matter energy-momentum tensor with respect to the metric tensor plays an important role in modified gravity theories with geometr…
Black hole solutions in the quadratic Weyl conformal geometric theory of gravity
Jin-Zhao Yang, Shahab Shahidi, Tiberiu Harko
We consider numerical black hole solutions in the Weyl conformal geometry, and its associated conformally invariant Weyl quadratic gravity. In this model Einstein gravity (with a p…
Palatini formulation of the conformally invariant gravity theory
Tiberiu Harko, Shahab Shahidi
We investigate the field equations of the conformally invariant models of gravity with curvature-matter coupling, constructed in Weyl geometry, by using the Palatini formalism. We…
Coupling matter and curvature in Weyl geometry: conformally invariant gravity
Tiberiu Harko, Shahab Shahidi
We investigate the coupling of matter to geometry in conformal quadratic Weyl gravity, by assuming a coupling term of the form , where is the ordinary matter…
Non-minimal geometry-matter couplings in Weyl-Cartan space-times: gravity
Tiberiu Harko, Nurgissa Myrzakulov, Ratbay Myrzakulov +1
We consider an extension of standard General Relativity in which the Hilbert-Einstein action is replaced by an arbitrary function of the Ricci scalar, nonmetricity, torsion, and th…
Cosmological evolution and dark energy in osculating Barthel-Randers geometry
Rattanasak Hama, Tiberiu Harko, Sorin V. Sabau +1
We consider the cosmological evolution in an osculating point Barthel-Randers type geometry, in which to each point of the space-time manifold an arbitrary point vector field is as…
Cosmological implications of Rastall- theory
Shahab Shahidi
Cosmological implications of a generalized Rastall theory where the non-conservation equation is promoted to accepts arbitrary functions of the Ricci scalar is considered. We have…
Anisotropy in constraint 4D Gauss-Bonnet gravity
Shahab Shahidi, Nima Khosravi
Recently a new 4D Einstein-Gauss-Bonnet theory has been introduced \textbf{[Phys. Rev. Lett. 124 (2020) 081301]} with a serious debate that it does not possess a covariant equation…
Non-minimal Energy-momentum squared gravity
Shahab Shahidi
We consider a gravitational theory with an additional non-minimal coupling between baryonic matter fields and geometry. The coupling is second order in the energy momentum tensor a…
Geodesic deviation, Raychaudhuri equation, Newtonian limit, and tidal forces in Weyl-type gravity
Jin-Zhao Yang, Shahab Shahidi, Tiberiu Harko +1
We consider the geodesic deviation equation, describing the relative accelerations of nearby particles, and the Raychaudhuri equation, giving the evolution of the kinematical quant…
Black hole solutions in modified gravity induced by quantum metric fluctuations
Jin-Zhao Yang, Shahab Shahidi, Tiberiu Harko +1
The inclusion of the quantum fluctuations of the metric in the geometric action is a promising avenue for the understanding of the quantum properties of gravity. In this approach t…
Weyl type gravity, and its cosmological implications
Yixin Xu, Tiberiu Harko, Shahab Shahidi +1
We consider an type gravity model in which the scalar non-metricity of the space-time is expressed in its standard Weyl form, and it is fully determined by a vec…
Distinguishing Brans-Dicke-Kerr type naked singularities and black holes with their thin disk electromagnetic radiation properties
Shahab Shahidi, Tiberiu Harko, Zoltán Kovács
The possible existence of naked singularities, hypothetical astrophysical objects, characterized by a gravitational singularity without an event horizon is still an open problem in…
Cosmology in theories with derivative matter coupling
Zahra Haghani, Shahab Shahidi
A new class of modified gravity theories with a healthy higher order derivative terms of a function of the matter Lagrangian is considered. Generally the energy momentum t…