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Inspired by recent studies of high-scale decay constant or flavorful QCD axions, we review and clarify their existence in effective string models with anomalous $U(1)$ gauge groups. We find that such models, when coupled to charged scalars…
It is argued that the precise three flavor symmetry of hadrons is not SU(3)_F but rather U(4)_F restricted to SU(2)_{ud}*SU(2)_{cs}*U(1) and considered in the limit of frozen charm degree of freedom. Within this scheme the only hypercharge…
A new suggestion for organizing the charged pseudo scalar mesons is presented. The simple Non-relativistic (NR) potential model employs a single value of the light quark mass and determines the potential coupling constant directly from the…
In the present work we study the effect of the scalar spin coupling of constituent quarks on the nucleon electroweak properties by introducing a valence light-front wave function with two momentum scales. By comparing the results obtained…
At low energies, the strong interaction is governed by the Goldstone bosons associated with the spontaneous chiral symmetry breaking, which can be systematically described by chiral perturbation theory. In this paper, we apply this theory…
The chiral constituent quark model ($\chi$CQM) has been extended to calculate the flavor structure of the nucleon through the meson-nucleon sigma terms which have large contributions from the quark sea and are greatly affected by chiral…
Using quenched chiral perturbation theory, we compute the long-distance behaviour of two-point functions of flavour non-singlet axial and vector currents in a finite volume, for small quark masses, and at a fixed gauge-field topology. We…
We study a deformation of N=2 supersymmetric QCD with U(N) gauge group and N_f quark flavors induced by the mass term \mu for the adjoint matter which breaks supersymmetry down to N=1 QCD. Recently this deformation was shown to lead to a…
Using the expansion of the baryon wave function in a series of products of single quark bispinors (Dirac orbitals), the nonsinglet axial and tensor charge of the nucleon are calculated. The leading term yields ${G_A}/{G_V} = 1.27$ and in…
Relativistic heavy ion collisions provide the possibility to study the topological charge in QCD matter through the event-by-event fluctuating net axial charge or nonequal numbers of left- and right-handed quarks they generate in the…
It follows on general grounds that the theta dependence in QCD is more complicated than suggested by the large N_c approach or instanton arguments. Generically, the vacuum energy E_{vac}(\theta) is a multi-valued function of \theta…
We show how quark-disconnected and quark-connected contributions to hadronic n-point functions can be written as independent correlators for which one can derive expressions in partially quenched chiral effective theory. As an example we…
With appropriate gauge transformations, field can replace electric charge in quarks. Classical quarks, in a necessary non-gauge invariant formulation, are used for illustration, bringing to the fore the limitations of the usual electric…
Flavor singlet combinations of quark operators ${\cal{O}}_S^{\Gamma} = \bar{u}\Gamma u + \bar{d}\Gamma d + \bar{s}\Gamma s$ contribute to many important physical observables in the low energy region of QCD. Experimentally one finds the…
We calculate the tensor and axial charges of the quark in the Schwinger-Dyson formalism of Landau gauge QCD. It is found that the dressed tensor and isovector axial charges of the quark are suppressed against the bare quark contribution,…
We discuss the general method of the calculation of the nucleon matrix elements of an operator associated with nonvalence quarks. The method is based on the QCD sum rules and low energy theorems. As an application of these considerations,…
We argue a smallness of gauge couplings in abelian quiver gauge theories, taking the anomaly cancellation condition into account. In theories of our interest there exist chiral fermions leading to chiral gauge anomalies, and an anomaly-free…
It is shown that the strong volume-dependence of the axial charge of the nucleon seen in lattice QCD calculations can be understood quantitatively in terms of the pion-induced interactions between neighbouring nucleons. The associated wave…
Like the axial vector charges, defined from the forward nucleon matrix element of the axial vector current on the light cone, the nucleon tensor charge, defined from the corresponding matrix element of the tensor current, is essential for…
The low-energy sector of QCD with $N_f = 2\!+\!1$ dynamical quark flavors at non-vanishing chemical potential and temperature is studied with a non-perturbative functional renormalization group method. The analysis is performed in different…