179 citations · 1k across the 58 of their papers we have counts for
33 papers · 1 filter
Exact Solutions for Chiral Gravitational Waves from Spin-2 Mixing
Mohammad Ali Gorji, Yuhang Zhu
A spectator spin-2 field can mix linearly with the metric tensor perturbations. We study the coupled tensor system in an inflationary background, including a parity violating effec…
Disformal Maps: Classification and Singular Dynamics
Mohammad Ali Gorji, Pavel Jiroušek, Alexander Vikman +1
Being agnostic about the field content of a gravitational system, we consider a general disformal transformation of the metric, , on a four-dimensional Lo…
Fragility of stealth solutions in mimetic gravity
Alireza Allahyari, Clarisse Donio, Mohammad Ali Gorji +2
We study a broad class of constrained mimetic-type extensions of general relativity with action , where i…
Abelian and non-Abelian mimetic black holes
Mohammad Ali Gorji, Susmita Jana, Pavel Petrov
We investigate black hole solutions in the mimetic extension of the Einstein-Yang-Mills system, in which the Yang-Mills term is constrained to be constant. In the Abelian U(1) case…
Imperfect dark matter with higher derivatives
Mohammad Ali Gorji
We introduce a higher-derivative action for dark matter whose energy-momentum tensor describes an imperfect fluid with nonzero pressure, energy flux, and anisotropic stress. In the…
Unique gravitational wave signatures of GLPV scalar-tensor theories
Guillem Domènech, Alexander Ganz, Mohammad Ali Gorji +1
We study gravitational waves induced by scalar primordial fluctuations in Gleyzes-Langlois-Piazza-Vernizzi (GLPV), beyond Horndeski, scalar-tensor theories. We uncover, at the leve…
Nonlinear gravitational waves in Horndeski gravity: Scalar pulse and memories
Jibril Ben Achour, Mohammad Ali Gorji, Hugo Roussille
We present and analyze a new non-perturbative radiative solution of Horndeski gravity. This exact solution is constructed by a disformal mapping of a seed solution of the shift-sym…
Disformal gravitational waves
Jibril Ben Achour, Mohammad Ali Gorji, Hugo Roussille
Contrary to conformal transformations, disformal transformations can change the principal null directions of a spacetime geometry. Thus, depending on the frame a gravitational wave…
Cosmological Perturbation Theory in Metric-Affine Gravity
Katsuki Aoki, Sebastian Bahamonde, Jorge Gigante Valcarcel +1
We formulate cosmological perturbation theory around the spatially curved FLRW background in the context of metric-affine gauge theory of gravity which includes torsion and nonmetr…
Primordial-tensor-induced stochastic gravitational waves
Mohammad Ali Gorji, Misao Sasaki
Cosmological stochastic gravitational waves (GWs) induced by a spectator field are usually expected to have an amplitude very small compared with those generated by the curvature p…
Cosmological memory effect in scalar-tensor theories
Mohammad Ali Gorji, Taisuke Matsuda, Shinji Mukohyama
The cosmological memory effect is a permanent change in the relative separation of test particles located in a FLRW spacetime due to the passage of gravitational waves. In the case…
Dark Matter from Entropy Perturbations in Curved Field Space
Hassan Firouzjahi, Mohammad Ali Gorji, Shinji Mukohyama +1
The accumulated energy density of the excited entropy modes in multiple field inflationary scenarios can play the role of dark matter. In the usual case of a flat field space witho…
Inflationary gravitational waves in consistent Einstein-Gauss-Bonnet gravity
Katsuki Aoki, Mohammad Ali Gorji, Shuntaro Mizuno +1
We study the slow-roll single field inflation in the context of the consistent Einstein-Gauss-Bonnet gravity that was recently proposed in \cite{Aoki:2020lig}. In addition…
Stealth dark energy in scordatura DHOST theory
Mohammad Ali Gorji, Hayato Motohashi, Shinji Mukohyama
A stealth de Sitter solution in scalar-tensor theories has an exact de Sitter background metric and a nontrivial scalar field profile. Recently, in the context of Degenerate Higher…
Cosmology and gravitational waves in consistent Einstein-Gauss-Bonnet gravity
Katsuki Aoki, Mohammad Ali Gorji, Shinji Mukohyama
In a very recent paper [1], we have proposed a novel -dimensional gravitational theory with two dynamical degrees of freedom, which serves as a consistent realization of …
A consistent theory of Einstein-Gauss-Bonnet gravity
Katsuki Aoki, Mohammad Ali Gorji, Shinji Mukohyama
We investigate the limit of the -dimensional Einstein-Gauss-Bonnet gravity, where the limit is taken with kept fixed and is the original…
Mimetic Black Holes
Mohammad Ali Gorji, Alireza Allahyari, Mohsen Khodadi +1
In this paper, we look for the vacuum static spherically symmetric solution in the mimetic gravity scenario based on the conformal invariance principle. The trivial solution is a s…
Cosmology in Mimetic SU(2) Gauge Theory
Mohammad Ali Gorji, Shinji Mukohyama, Hassan Firouzjahi
It is well known that the standard scalar field mimetic cosmology provides a dark matter-like energy density component. Considering gauge symmetry, we study the gauge field…
Two-field disformal transformation and mimetic cosmology
Hassan Firouzjahi, Mohammad Ali Gorji, Seyed Ali Hosseini Mansoori +2
We extend the disformal transformation to models with two scalar fields and look at its singular limit. Solving the eigentensor equation for the Jacobian of the transformation of t…
Photon gas thermodynamics in dS and AdS momentum spaces
M. A. Gorji, V. Hosseinzadeh, K. Nozari +1
In this paper, we study thermostatistical properties of a photon gas in the framework of two deformed special relativity models defined by the cosmological coordinatizations of the…
Late time cosmic acceleration from natural infrared cutoff?
Mohammad Ali Gorji
In this paper, inspired by the ultraviolet deformation of the Friedmann-Lema\^ıtre-Robertson-Walker geometry in loop quantum cosmology, we formulate an infrared-modified cosmologic…
Gravity's rainbow: a bridge between LQC and DSR
M. A. Gorji, K. Nozari, B. Vakili
The doubly special relativity (DSR) theories are investigated in order to take into account an observer-independent length scale in special relativity framework. It is widely belie…
Early universe thermostatistics in curved momentum spaces
M. A. Gorji, V. Hosseinzadeh, K. Nozari +1
The theories known as doubly special relativity are introduced in order to take into account an observer-independent length scale and the speed of light in the framework of special…
Bounds on quantum gravity parameter from the NJL effective model of QCD
K. Nozari, M. Khodadi, M. A. Gorji
Existence of a minimal measurable length, as an effective cutoff in the ultraviolet regime, is a common feature of all approaches to the quantum gravity proposal. It is widely beli…