Related papers: Instantons in QCD with Many Colors
We study the scaling with the number of colours, $N_c$, of the weak amplitudes mediating kaon mixing and decay. We evaluate the amplitudes of the two relevant current-current operators on the lattice for $N_c=3-7$. We conclude that the…
We investigate the temperature dependence of the instanton contents of gluon fields, using unquenched lattice QCD and the cooling method. The instanton size parameter deduced from the correlation function decreases from 0.44fm below the…
Resonances and enhancements in meson-meson scattering can be divided into two classes distinguished by their behavior as the number of colors N_c in QCD becomes large: The first are ordinary mesons that become stable as N_c goes to…
We study the scaling with the number of colors $N_c$ of the weak amplitudes mediating kaon mixing and decay, in the limit of light charm masses ($m_u=m_d=m_s=m_c$). The amplitudes are extracted directly on the lattice for $N_c = 3-7$ (with…
The anomalous scaling behavior of the topological susceptibility $\chi_t$ in two-dimensional $CP^{N-1}$ sigma models for $N\leq 3$ is studied using the overlap Dirac operator construction of the lattice topological charge density. The…
Instanton calculations in QCD are generically plagued by infrared divergencies associated with the integration over the instanton size $\rho$. Here, we demonstrate explicitly that the typical inverse hard momentum scale ${\mathcal Q}^{-1}$…
We present an update on the study of topological structure of QCD. Issues addressed include a comparison between the plaquette and the geometric methods of calculating the topological density. We show that the improved gauge action based on…
In the limit of a large number of colors (N), both Yang-Mills and quantum chromodynamics are expected to have a first-order phase transition separating a confined hadronic phase and a deconfined plasma phase. One aspect of this separation…
The influence of nonperturbative fields on instantons in quantum chromodynamics is studied. Nonperturbative vacuum is described in terms of nonlocal gauge invariant vacuum averages of gluon field strength.Effective action for instanton is…
We present a method for ordering two-nucleon interactions based upon their scaling with the number of QCD colors, $N_c$, in the limit that $N_c$ becomes large. Available data in the two-nucleon sector shows general agreement with this…
We show that $QCD_2$ with adjoint fermions involves instantons due to nontrivial $\pi_1[SU(N)/Z_N]~=~Z_N$. At high temperatures, quasiclassical approximation works and the action and the form of effective (with account of quantum…
The QCD sum rule for the correlator of topological charge densities and related to it longitudinal part of the correlator of singlet axial currents is considered in the framework of instanton model. The coupling constant of eta'-meson with…
We comment on the recent paper (hep-lat/0005006) by Isgur and Thacker on the origin of the OZI rule in QCD. We show that instantons explain the sign and magnitude of the observed OZI-violating amplitude in all mesonic channels, not just in…
At very high energies or small values of Bjorken x, the density of partons, per unit transverse area, in hadronic wavefunctions becomes very large leading to a saturation of partonic distributions. When the scale corresponding to the…
The standard first-order inelastic correction (IC) well known in the pre-QCD era, causes a rising $Q^2$-dependence of nuclear transparency in the quasielastic electron scattering, $A(e,e'p)A'$, at moderate $Q^2$, similar to what is supposed…
At zero density, the `t Hooft large N_c limit often provides some very useful qualitative insights into the non-perturbative physics of QCD. However, it is known that at high densities the `t Hooft large N_c world looks very different from…
The known calculations of the fermion condensate $<\bar{\psi}\psi>$ and the correlator $<\bar{\psi}\psi(x) ~\bar{\psi}\psi(0)>$ have been interpreted in terms of {\em localized} instanton solutions minimizing the {\em effective} action.…
We investigate the distribution of instanton sizes in the framework of a simplified model for ensembles of instantons. This model takes into account the non-diluteness of instantons. The infrared problem for the integration over instanton…
The singlet coupling to the topological charge density in the instanton vacuum, causes the instantons and antiinstantons to be screened over distances of the order of 1/2 fm. Dilute instanton systems behave as a free gas, while dense…
This paper focuses on the scaling of the S-matrix for elastic nucleon-nucleon scattering at large Nc. It is argued that the logarithm of a typical S-matrix element is proportional to Nc in the regime where the large Nc limit is taken with…