arXiv subjects

Shahin Mamedov

Publications and source records attributed to Shahin Mamedov.

At least 19 recordsLinked to original sources

arXiv2026

A winding number analysis of Schwarzschild black hole stability in light of Planck-scale modified kinematics

Determining whether Planck-scale effects can stabilize black holes addresses fundamental questions about black hole evaporation and quantum gravity consistency. Here, we analyze the thermodynamic topology of Schwarzschild black holes under Planck-scale modified kinematics, using a cubic entropy correction derived from a well-known phenomenological MDR with leading correction $ηE^3/E_P$. Enforcing physical constraints ($S'(r_h) > 0$, $T > 0$) via the entropy-geometry correspondence, we find a single unstable branch with $w = -1$ and $W = -1$ for both signs of the correction parameter. A second root suggesting stability ($w = +1$) is excluded due to negative mass/temperature and lies outside the perturbative regime. Thus, this class of MDRs does not yield stable Schwarzschild black holes. However, MDRs with different leading-order corrections may behave otherwise, leaving the search for Planck-scale stabilization an open endeavor.

gr-qc↗

arXiv2026

Schwarzschild-like Black Holes Submerged in an Exponential Density Dark Matter Profile

We study a class of Schwarzschild black holes embedded in an exponential-spheroidal dark matter halo, modelled by a phenomenological density profile $ρ(r)=ρ_0 e^{-r/r_0}$. By solving the Einstein equations for a static, spherically symmetric spacetime, we obtain an analytic solution for the lapse function that reduces to the Schwarzschild spacetime in the absence of the halo and to a regular halo configuration when the central black hole mass vanishes. Indeed, the two halo parameters, $ρ_0$ and $r_0$, describe the strength and radial extent of the dark matter distribution. We analyse the curvature structure, energy conditions, shadow observables, scalar quasi-normal modes and grey-body bounds of the resulting spacetime. The Ricci scalar and the Ricci square remain finite at the origin, whilst the Kretschmann scalar retains the usual central tidal singularity in the presence of a black hole mass. The weak, null, and dominant energy conditions are satisfied, whilst the strong energy condition is violated on a finite radial interval. We also show that the halo monotonically shifts the photon sphere and the shadow radius, which allows us to derive approximate constraints from the EHT observations of M87* and Sgr A*. For scalar perturbations, the Padé-resummed WKB approximation yields stable quasinormal frequencies, while the standard WKB approximation becomes unreliable for higher overtones and strong-halo configurations. Finally, the greybody bounds indicate that the halo weakens transmission through the effective barrier, particularly at low frequencies.

gr-qc↗

arXiv2026

Generalized parton distributions of a deuteron in an AdS/QCD hard-wall model

We investigate the gravitational form factors (GFFs) and the generalized parton distributions (GPDs) of the deuteron within the framework of the hard-wall AdS/QCD model. The momentum dependence of the GFFs obtained here is in good agreement with the results of the soft-wall AdS/QCD model. The value of the gravitational mean square radius in this model agrees with the experimental data. GFFs provide a holographic description of the. Deuteron GPDs are obtained from GFFs via sum rules and have shapes of plots similar to those for GPDs extracted from the electromagnetic form factors (EFFs) calculated in the framework of the soft-wall AdS/QCD model.

hep-ph↗

arXiv2026

Rotating Black Holes Surrounded by Massive Vector Fields in Kaluza Klein Gravity

In this paper, we introduce a rotating Kaluza-Klein black hole characterized by a massive vector field and a scalar field. We begin by identifying the horizons and mapping the allowed parameter space to differentiate black hole solutions from naked singularities. The thermodynamic analysis shows a phase transition by examining Hawking temperature and heat capacity. We also conduct a topological study of the thermodynamic potentials. The Hawking temperature indicates a conventional critical point, while the off-shell generalized free energy classifies the system into a specific universal group. We further investigate the geometry of the ergosphere and how it relates to the black holes spin. Additionally, we look at astrophysical signs, such as the black hole shadow and the features of the thin accretion disk. Our results indicate that while the extra-dimensional changes significantly shift phase transition points and modify the shadow size, the essential topological class remains stable. This study provides a solid framework for distinguishing higher-dimensional gravity models through both thermodynamic and observational signs.

gr-qc↗

arXiv2026

Solution of the boundary problem for the axial-vector field in the hard-wall AdS/QCD model

We solve an equation of motion for the axial-vector field under boundary conditions of the bulk-to-boundary propagator in the framework of the hard-wall model of AdS/QCD. The equation is reduced to the form of a homogeneous ordinary differential equation with varying coefficients. We solve conjugate equations and find fundamental solutions. This allows us to establish main relations and necessity conditions. The integral equation has both Volterra and Fredholm terms and was solved by the iteration method. We apply a new scheme to solve the equation, since all linearly independent necessary conditions for the existence of a solution were defined and used to establish a sufficient condition for Fredholm solvability of the problem.

hep-ph↗

arXiv2025

Quasinormal Modes and Topological Characteristics of a Schwarzschild Black Hole Surrounded by the Dehnen Type Dark Matter Halo

In this work, we explore the critical parameters that delineate the existence of black holes, identifying the permissible ranges that facilitate their formation. A comprehensive thermodynamic analysis of black holes is conducted, leading to the calculation of black hole remnants. We investigate the trajectory of light, establishing an upper limit for the parameters based on Event Horizon Telescope (EHT) observations of Sgr A*, ensuring that the black hole's shadow resides within the allowed region. Furthermore, we derive the quasinormal modes (QNMs) for both scalar and electromagnetic perturbations. Utilizing a topological framework, we examine the stability of the photon sphere and classify the topology of the black hole in accordance with its thermodynamic potentials.

gr-qc↗

arXiv2025

Electromagnetic transition form factors of nucleons from the hard-wall AdS/QCD model

The electromagnetic transition form factors for the transition between the ground and excited states of nucleons are studied in the framework of the hard-wall model of AdS/QCD. The profile functions of the spinor and vector fields in the bulk of AdS space are presented. Using AdS/CFT correspondence between the generating functions in the bulk and boundary theories an expression for the transition form factors are obtained from the bulk action for the interaction between the photon and nucleon fields. We consider the R(1710, 1535, 1440)\rightarrow N transitions and plot the Dirac and Pauli form factor dependencies on transferred momentum square. Also, the spiral amplitudes for these transitions are presented.

hep-ph↗

arXiv2025

Deuteron gravitational form factors, generalized parton distributions, and charge density in the framework of the soft-wall AdS/QCD model

We study the deuteron gravitational form factors (GFFs) and generalized parton distributions (GPDs) within the soft-wall AdS/QCD model, where deuteron is described by the bulk vector field with twist $τ=6$. For the finite-temperature studies, we apply the soft-wall model, which is thermalized by introducing a thermal dilaton field. GPDs and charge density are considered in impact parameter (IP) space and at zero and finite temperatures. We plot the temperature dependence of these quantities in IP space and observe a decreasing of their peaks on temperature increasing. The gravitational root means squared radius obtained here is close to the range given by experimental data for the mass radius and has low sensitivity to the temperature.

hep-ph↗

arXiv2023

Tensor meson couplings in AdS/QCD

We study the hadronic and radiative couplings of the $f_2(1270)$ meson within the hard- and soft-wall models of AdS/QCD. The results for the tensor meson-nucleon-nucleon coupling ($g_{f_2NN}$) and tensor meson-photon-vector meson coupling ($g_{f_2γρ}$) are compared to the ones obtained by using the dispersion relations and amplitude methods, respectively. Qualitative agreement with different analyses implies the reliability of the holographic description of spin-2 meson.

hep-ph↗

arXiv2023

Axial-vector form factor of nucleons at finite temperature from the AdS/QCD soft-wall model

The axial-vector form factor of the nucleons is studied at a finite temperature using the holographic soft-wall model with the thermal dilaton field. We use the bulk interaction action known from the zero temperature case and apply the profile functions of fields thermalized by the interaction with the thermal dilaton field. The dependence of the axial form factor on the square of the transferred momentum and the temperature is plotted for the ground and excited states of the nucleons.

hep-ph↗

arXiv2023

Vector Meson Gravitational Form Factors and Generalized Parton Distributions at finite temperature within the soft-wall AdS/QCD Model

We investigate the vector meson's gravitational form factors (GFFs) and generalized parton distributions (GPDs) at finite temperatures within the soft-wall AdS/ QCD model. The plotted soft-wall GFFs graphs at zero temperature are close to the hard-wall results [1]. The dependence on temperature of the GFFs and GPDs is studied using the thermal dilaton approach in the soft-wall model. Plots of thermal GFFs show that they decrease in temperature increase. Also, the gravitational radius of $ρ$ meson decreases in temperature growth and becomes zero around the critical temperature $T_c=0.2 {\rm\ GeV}$. GPDs at zero skewness are plotted and analyzed at zero and finite temperature cases.

hep-ph↗

arXiv2023

The magnetic properties of a deuteron $r_m$ from the AdS/QCD hard-wall model

The deuteron is a spin1 particle and due to current conservation and the P and C invariance of the EM interaction, it has three EM form factors in the one photon exchange (OPE) approximation, which include the charge GC(Q2), quadrupole GQ(Q2) and magnetic GM(Q2) form factors and was calculated in [1, 2, 3] at a zero temperature within soft-wall and hard-wall models AdS/QCD. In this work, we numerically calculated the deuteron magnetic radius RM in the framework of the hard-wall model of AdS/QCD and compare our results with the experimental data and soft-wall model results [2]

hep-ph↗

arXiv2023

The deuteron charge radıus $r_c$ in the framework of the hard-wall AdS/QCD model

We study the deuteron charge radius in the framework of a hard-wall AdS/QCD model. We present basic elements of the hard-wall model and write metrics for the AdS space. We introduce a vector field with twist $τ=6$ describing deuteron in the bulk of AdS space and other vector fields to describe photon respectively, write an effective action for the bulk fields interactions, find a $G_1(Q^2)$, $G_2(Q^2)$ and $G_3(Q^2)$ form factors, then quadrupole $G_Q(Q^2)$ and charge $G_C(Q^2)$ form-factors of a deuteron. Thus, from the charge $G_C(Q^2)$ form factor we find the deuteron charge radius $R_C$ in the framework of a hard-wall AdS/QCD model. Then we compare our result with the results soft-wall model and experimental data.

hep-ph↗

arXiv2023

Deuteron electromagnetic form factors and tensor polarization observables in the framework of the hard-wall AdS/QCD model

We study the electromagnetic form factors and tensor polarization observables of the deuteron in the framework of the hard-wall AdS/QCD model. We find a profile function for the bulk twist $τ=6$ vector field, which describes the deuteron on the boundary and fix the infrared boundary cut-off of AdS space in accordance with the ground state mass of the deuteron. We obtain the deuteron charge monopole, quadrupole, and magnetic dipole form factors and tensor polarization observables from the bulk Lagrangians for the deuteron and photon field interactions. We plot the momentum transfer dependence of the form factors and tensor polarization observables and compare our numerical results with those in the soft-wall model and experimental data.

hep-ph↗

arXiv2022

Axial-vector form factor of nucleons in the isospin medium from the hard-wall AdS/QCD model

We study the axial-vector form factor of the nucleons at constant and homogenous isospin chemical potential using holographic QCD. Nucleon mass splitting in such isospin medium is taken into account. According to AdS/CFT correspondence, the critical value of the isospin chemical potential μ_I equals to UV- boundary value of the time component of the bulk gauge field. We calculate the axial-vector form factor of the proton and neutron in such background in the framework of the hard-wall model and plot the form factors for the isospin chemical potential critical value μ_I=m_π.

hep-ph↗

arXiv2022

$a_{1}$ meson-nucleon coupling constant at finite temperature from the soft-wall AdS/QCD model

We study the temperature dependence of the $a_1$ meson-nucleon coupling constant in the framework of the soft-wall AdS/QCD model with thermal dilaton field. Profile functions for the axial-vector and fermion fields in the AdS-Schwarzschild metric are presented. It is constructed an interaction Lagrangian for the fermion-axial-vector-thermal dilaton fields system in the bulk of space-time. From this Lagrangian integral representation for the $g_{a_1NN}$ coupling constant is derived. The temperature dependence of this coupling constant is numerically analyzed.

hep-ph↗

arXiv2021

Temperature dependence of $ρ$ meson-nucleon coupling constant from the AdS/QCD soft-wall model

We investigate the dependence of the $ρ$ meson-nucleon coupling constant on the temperature of the medium using the soft-wall model of AdS/QCD. The finite temperature profile functions for the vector and fermion fields are applied to the model having a thermal dilaton field. The interaction Lagrangian in the bulk between these fields is written as in zero temperature case and includes minimal- and magnetic-type interactions. The temperature dependence of the $g_{ρNN}(T)$ coupling constant and its terms are plotted. We observe that the coupling constant and its separate terms become zero at the medium temperature near the Hawking temperature of phase transition.

hep-ph↗

arXiv2020

$a_1$ meson-baryon coupling constants in the framework of soft-wall and hard-wall AdS/QCD models

We calculate the $a_1$ meson-nucleon coupling constant in the framework of soft-wall and hard-wall AdS/QCD models. In the bulk of AdS space were written bulk interaction Lagrangians for a minimal gauge coupling, a magnetic gauge coupling and a triple coupling. To use AdS/CFT correspondence and these bulk interaction Lagrangians we calculate the $a_1$ axial-vector meson-nucleon coupling constant in the boundary of AdS space within both models. We observe that the numerical values for the $g_{a_1 NN}$ coupling constant in the framework of both models are more close to the experimental value than results in other works. We also calculate the $g_{a_1 ΔΔ}$ axial-vector meson-$Δ$-baryon coupling constant in the framework of hard-wall AdS/QCD model.

hep-ph↗