arXiv subjects

Shahin Mamedov

Publications and source records attributed to Shahin Mamedov.

26 records · Page 2Linked to original sources

arXiv2017

Nucleon's axial-vector form factor in the hard-wall AdS/QCD model

The axial-vector form factor of the nucleons is considered in the framework of hard-wall model of holographic QCD. A new interaction term between the bulk gauge and matter fields was included into the interaction Lagrangian. We obtain the axial-vector form factor of nucleons in the boundary QCD from the bulk action using AdS/CFT correspondence. The momentum square dependence of the axial-vector form factor is analysed numerically.

hep-th↗

arXiv2016

Meson effective mass in the isospin medium in hard-wall AdS/QCD model

We study a mass splitting of light vector, axial-vector and pseudoscalar mesons in isospin medium in the framework of hard-wall model. We write an effective mass definition for the interacting gauge fields and scalar field introduced in gauge field theory in the bulk of AdS space-time. Relying on holographic duality we obtain a formula for the effective mass of a boundary meson in terms of derivative operator over the extra bulk coordinate. The effective mass found in this way coincides with the one obtained from finding of poles of the two-point correlation function. In order to avoid introducing distinguished infrared boundaries in the quantisation formula for the different mesons from the same isotriplet we introduce extra action terms at this boundary, which reduces distinguished values of this boundary to the same value. Profile function solutions and effective mass expressions were found for the in-medium $ρ$, $a_1$ and $π$ mesons.

hep-th↗

arXiv2015

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

In the framework of the soft-wall model of AdS/QCD we calculated the $ρ$ meson nucleon coupling constant. Bulk-to boundary propagators for the free vector and spinor fields are presented, whose boundary values correspond to $ρ$ meson and to the nucleon respectively. The interaction Lagrangian between these fields is written in the bulk of AdS space and includes magnetic type interactions as well. Using the AdS/CFT correspondence from the bulk interaction action we derived the $g_{ρNN}$ coupling constant in the boundary QCD. We found that the soft-wall model result for the $g_{ρNN}$ constant is more close to empirical values than the one obtained in the hard-wall model.

hep-th↗

arXiv2014

Nucleon mass splitting in the isospin medium

Using the AdS/CFT correspondence, we investigate a nucleon mass splitting and nucleon-pion coupling in the isospin medium. We find that there exists a nucleon mass splitting which is exactly given by the half of the meson mass splitting because nucleon has the half isospin charge of the charged mesons. In addition, we also investigate the nucleon-pion coupling, which requires the modification of the known Abelian-type unitary gauge fixing term because non-Abelian fluctuations should be taken into account in the isospin medium. In this paper, after constructing an appropriate unitary gauge fixing term, we find that in spite of the nucleon's and meson's mass splittings, there is no nucleon-pion coupling splitting in the isospin medium.

hep-th↗

arXiv2013

Holographic meson mass splitting in the Nuclear Matter

We study the holographic light meson spectra and their mass splitting in the nuclear medium. In order to describe the nuclear matter, we take into account the thermal charged AdS geometry with two flavor charges, which can be reinterpreted as the number densities of proton and neutron after some field redefinitions. We show that the meson mass splitting occurs when there exists the density difference between proton and neutron. Depending on the flavor charge, the mass of the positively (negatively) charged meson increases (decreases) as the density difference increases, whereas the neutral meson mass is independent of the density difference. In the regime of the large nucleon density with a relatively large number difference between proton and neutron, we find that negatively charged pion becomes massless in the nuclear medium, so the pion condensate can occur. We also investigate the binding energy of a heavy quarkonium in the nuclear medium, in which the binding energy of a heavy quarkonium becomes weaker as the density difference increases.

hep-th↗

arXiv2011

Electromagnetic interaction vertex of $Δ$ baryons in hard-wall AdS/QCD model

We consider an interaction of a spin-3/2 field with the electromagnetic field in the framework of the hard-wall model of AdS/QCD. We write Lagrangian for this interaction including all kinds interaction terms in the bulk of AdS$_{5}$ space and present the scattering matrix element in integrals over the fifth coordinate. Comparing the current matrix element obtained in the boundary of this space with the one known from field theory, we find the vertex function coefficients for the $γ^{*}ΔΔ$ interaction vertex. As an example, we apply the obtained coefficients to the computation of the charge form factor $G_{E0}$ for the $Δ^{+}$ baryon and compare the result with the one obtained in the field theory.

hep-ph↗

arXiv2010

Energy spectrum of simply constant chromoelectric flux tubes

In this article we obtain the energy spectrum of colored, spinor particles in chromoelectric flux tubes. The chromoelectric field of the flux tubes considered here comes from {\em simply} constant gauge potentials rather than from covariantly constant gauge potential, as is usually the case. The energy spectrum of the simply constant flux tubes is different than that of the covariantly constant flux tubes. The spectrum is discrete due to the walls of the tube and with a plus/minus constant shift depending on the magnitude of the constant chromoelectric background. This goes against the classical intuition where one would expect a charged particle in a uniform "electric" field to accelerate with ever increasing velocity/energy i.e. there would be no constant energy eigenvalue.

hep-th↗

arXiv2007

AdS/CFT correspondence via R-current correlation functions revisited

Motivated by realizing open/closed string duality in the work by Gopakumar [Phys. Rev. D70:025009,2004], we study two and three-point correlation functions of R-current vector fields in N=4 super Yang-Mills theory. These correlation functions in free field limit can be derived from the worldline formalism and written as heat kernel integrals in the position space. We show that reparametrizing these integrals converts them to the expected AdS supergravity results which are known in terms of bulk to boundary propagator. We expect that this reparametrization corresponds to transforming open string moduli parameterization to the closed string ones.

hep-th↗