arXiv subjects

Younes Younesizadeh

Publications and source records attributed to Younes Younesizadeh.

4 recordsLinked to original sources

arXiv2026

Modified Gravity Framework for the Woods-Saxon Inflation: Theoretical Foundations and Observational Constraints

We investigate an inflationary scenario within a modified gravity theory that extends the Einstein-Hilbert action through a non-minimal coupling between the inflaton $ϕ$ and the trace of the energy-momentum tensor $T$. This $f(ϕ)T$ framework is designed to naturally recover the standard general relativity in the post-inflationary universe. Within this theory, we apply the Woods-Saxon potential. The slow-roll dynamics yields a luminal sound speed $c_s^2=1$ for our specific choice of the coupling function. For the model parameters $a \lesssim 1$ and the modest coupling $β=0.1$, we obtain a scalar spectral index $n_s\approx0.959$--$0.966$ and a tensor-to-scalar ratio $r<0.01$, which reveal a good agreement with the latest Planck and BICEP/Keck data on the $(n_s, r)$ constraints. Crucially, we shall demonstrate that the $f(ϕ)T$ coupling is essential for the observational viability of the model with respect to the CMB two-point statistics. This work establishes a viable inflationary scenario within the scope of the inflationary observables which are considered here.

gr-qc↗

arXiv2022

Gravitational lensing and shadow of charged black holes in the low-energy limit of string theory

In this work, we investigate the shadow cast and strong field gravitational lensing of a new class of black hole solutions in dilaton gravity where dilaton field is coupled with nonlinear Maxwell invariant [Younesizadeh et al. in Int J Mod Phys A 34(35):1950239]. The space-time is a stationary axisymmetric geometry. The key part in our investigations is finding the effect of dilaton parameter N on the size of shadows and the energy emission rate. As the N parameter increases, the size of black hole shadow increases. Also, the energy emission rate increases with increase in the dilaton parameter N. By supposing the gravitational field of the supermassive object at the heart of Milky Way galaxy described by this metric, we estimated the numerical values of the observables for gravitational lensing in the strong field limit.

hep-th↗

arXiv2020

A New Black Hole Solution In Dilaton Gravity Inspired By Power-Law Electrodynamics

In this work, a new class of slowly rotating black hole solutions in dilaton gravity has been obtained where dilaton field is coupled with nonlinear Maxwell invariant. The background space-time is a stationary axisymmetric geometry. Here, it has been shown that the dilaton potential can be written in the form of generalized three Liouville-type potentials. In the presence of this three Liouville-type dilaton potential, the asymptotic behavior of the obtained solutions are neither flat nor (A)dS. One bizarre property of the electric field is that the electric field goes to zero when $r\rightarrow 0$ and diverges at $r\rightarrow\infty$. We show the validity of the first law of thermodynamics in thermodynamic investigations. The local and global thermodynamical stability are investigated through the use of heat capacity and Gibbs free-energy. Also, the bounded, phase transition and the Hawking-Page phase transition points as well as the ranges of black hole stability have been shown in the corresponding diagrams. From these diagrams, we can say that the presence of the dilaton field makes the solutions to be locally stable near origin and vanishes the global stability of our solutions. In final thermodynamics analysis, we obtain the Smarr formula for our solution. We will show that the presence of dilaton field brings a new term in the Smarr formula. Also, we find that the dilaton field makes the black hole(AdS) mass to decrease for every fix values of S(entropy).

hep-th↗

arXiv2018

Anyon Black Holes

We propose a correspondence between an Anyon Van der Waals fluid and a (2+1) dimensional AdS black hole. Anyons are particles with intermediate statistics that interpolates between a Fermi-Dirac statistics and a Bose-Einstein one. A parameter $α$ ($0<α<1$) characterizes this intermediate statistics of Anyons. The equation of state for the Anyon Van der Waals fluid shows that it has a quasi Fermi-Dirac statistics for $α> α_c$, but a quasi Bose-Einstein statistics for $α< α_c$. By defining a general form of the metric for the (2+1) dimensional AdS black hole and considering the temperature of the black hole to be equal with that of the Anyon Van der Waals fluid, we construct the exact form of the metric for a (2+1) dimensional AdS black hole. The thermodynamic properties of this black hole is consistent with those of the Anyon Van der Waals fluid. For $α< α_c$, the solution exhibits a quasi Bose-Einstein statistics. For $α> α_c$ and a range of values of the cosmological constant, there is, however, no event horizon so there is no black hole solution. Thus, for these values of cosmological constants, the AdS Anyon Van der Waals black holes have only quasi Bose-Einstein statistics.

hep-th↗