Axial Vector-Meson–Nucleon Interaction Constant in the AdS/QCD Soft Wall Model

Russian Physics Journal - This work investigates the interaction of an axial vector-meson with nucleons in the AdS/QCD soft wall model. The axial vector fields have been determined inside the...     

A Diquark-Quark Model with Its Use in Nucleon Form Factorst

The nucleon electromagnetic form factors are investigated within a simple diquark-quark model using the light-front formalism. In this model, baryon is described as a bound state of one quark and one clustering diquark. The calculational results are compared with the experimental ones. We also regard the quarks in a baryon as pointlike constituent quarks.     

In-Medium Nucleon Electromagnetic Form Factors in Vector Meson Dominance Model

We study medium modifications of the nucleon electromagnetic form factors in the vector meson dominance model. The in-medium vector meson masses are taken from a chiral SU(3) model. We find that the electric and magnetic form factors of the bound nucleon deviate considerably from those of the free nucleon. Our results are comparable to the results from the quark meson coupling model approach and are consistent with present experimental limits.     

What’s the point? Hole-ography in Poincaré AdS

In the context of the AdS/CFT correspondence, we study bulk reconstruction of the Poincaré wedge of AdS\(_3\) via hole-ography, i.e., in terms of differential entropy of the dual CFT\(_2\). Previous work had considered the reconstruction of closed or open spacelike curves in global AdS, and of infinitely extended spacelike curves in Poincaré AdS that are subject to a periodicity condition at infinity. Working first at constant time, we find that a closed curve in Poincaré is described in the CFT by a family of intervals that covers the spatial axis at least twice. We also show how to reconstruct open curves, points and distances, and obtain a CFT action whose extremization leads to bulk points. We then generalize all of these results to the case of curves that vary in time, and discover that generic curves have segments that cannot be reconstructed using the standard hole-ographic construction. This happens because, for the nonreconstructible segments, the tangent geodesics fail to be fully contained within the Poincaré wedge. We show that a previously discovered variant of the hole-ographic method allows us to overcome this challenge, by reorienting the geodesics touching the bulk curve to ensure that they all remain within the wedge. Our conclusion is that all spacelike curves in Poincaré AdS can be completely reconstructed with CFT data, and each curve has in fact an infinite number of representations within the CFT.     

Nucleon—Nucleon Phase Shifts in the Extended Quark—Delocalization Colour—Screening Model

An alternative method is applied to the study of nocleon-nucleon scattering phase shifts within the framework of the extended quark delocalization colour-screening model,in which the one-pion exchange with short-range cutoff is included.     

Nucleon Form Factors and N-△ Transitions in a Hypercentral Constituent Quark Model with Meson Cloud

We study the nucleon form factors and the nucleon-△（1232） transitions in a framework of hypercentral constituent quark model. The pion meson cloud effect is taken into account explicitly. Our results show that the pion cloud contributes substantially to the nucleon form factors as well as to the helicity amplitudes of △（1232）, and it gives an improved agreement compared to the experimental.     

Structure of the Gauge Invariant Quark Green’s Function in QCD2

We study, in two-dimensional QCD and in the large-N _c limit, the properties of the gauge invariant quark Green’s function, defined with a path-ordered phase factor along a straight line. The analysis is done by means of an exact integrodifferential equation. The Green’s function is found to be infrared finite, with singularities represented by an infinite number of threshold type branch points with a power ?3/2, starting at positive mass squared values. Its expression is analytically determined.     

On the CHSH Form of Bell’s Inequalities

A common mistake present in the derivation of the usually known as the CHSH form of Bell’s inequalities is pointed out. References and comments to the correct approach are given. This error does not alter the final result and only affects the logical consistency of the derivation, but since it seems to be a widespread misconception regarding the roll and interpretation of the of use of hidden variables in Bell’s theorem it is considered to be of general interest.     

Δ -resonances: Quark models, chiral symmetry and AdS/QCD

The mass spectrum of Δ -resonances is compared to predictions based on three quark-model variants, to predictions assuming that chiral symmetry is restored in high-mass baryon resonances, and to predictions derived from AdS/QCD. The latter approach yields a nearly perfect agreement when the confinement property of QCD is modeled by a soft wall in AdS.     

Transition Electromagnetic Form Factor in the Minkowski Space Bethe–Salpeter Approach

Using the solutions of the Bethe–Salpeter equation in Minkowski space for bound and scattering states found in previous works, we calculate the transition electromagnetic form factor describing the electro-disintegration of a bound system.     

Charge Splitting in πNΔ Form Factor

Physics of Atomic Nuclei - Experimental data on πN scattering in the elastic energy region w ≤ 1.45 GeV are analyzed within the K-matrix approach with effective lagrangians. The charge...     

γ * ρ 0→π 0 transition form factor in extended AdS/QCD models

The γ ^* ρ ⁰→π ⁰ transition form factor is extracted from recent result for the γ ^* γ ^* π ⁰ form factor obtained in the extended hard-wall AdS/QCD model with a Chern–Simons term. In the large momentum region, the form factor exhibits a 1/Q ⁴ behavior, in accordance with the perturbative QCD analysis, and also with the Light-Cone Sum Rule (LCSR) result if the pion wave function exhibits the same endpoint behavior as the asymptotic one. The appearance of this power behavior from the AdS side and the LCSR approach seem to be rather similar: both of them come from the “soft” contributions. Comparing the expressions for the form factor in both sides, one can obtain the duality relation $z\propto \sqrt{u(1-u)}$ , which is compatible with one of the most important relations of the Light-Front holography advocated by Brodsky and de Teramond. In the moderate Q ² region, the comparison of the numerical results from both approaches also supports a asymptotic-like pion wave function, in accordance with previous studies for the γ ^* γ ^* π ⁰ form factor. The form factor at zero momentum transfer gives the γ ^* ρ ⁰ π ⁰ coupling constant, from which one can determine the partial width for the ρ ⁰(ω)→π ⁰ γ decay. We also calculate the form factor in the time-like region, and study the corresponding Dalitz decays ρ ⁰(ω)→ π ⁰ e ⁺ e ^?, π ⁰ μ ⁺ μ ^?. Although all these results are obtained in the chiral limit, numerical calculations with finite quark masses show that the corrections are extremely small. Some of these calculations are repeated in the Hirn–Sanz model and similar results are obtained.     

Chemical Potential Dependence of the Dressed-Quark Propagator in a Simple Confining QCD Model

Based on the Dyson-Schwinger approach, a method for obtaining the chemical potential dependence of the dressed quark propagator in the ‘Nambu-Goldstone‘ and the ‘Wigner‘ phase is developed. The bag constant in the presence of the non-zero chemical potential is analysed.     

Model of impurity distribution in the atmosphere for a source above the Earth’s surface

Taking into account diffusion and wind transport processes, a model of the distribution of an impurity polluting the Earth’s atmosphere was constructed. On its basis, simple formulas were derived, which, using gas-correlation IR radiometry, allow the estimation of the power and position of impurity sources above the Earth’s surface.