Related papers: Direct instantons, topological charge screening an…
Instanton effects and three-loop perturbative contributions are incorporated into QCD sum-rule analyses of pseudoscalar ($J^{PC}=0^{-+}$) gluonium. Gaussian sum-rules are shown to be superior to Laplace sum-rules in optimized predictions…
The Drell-Hearn-Gerasimov and Bjorken sum rules are special examples of dispersive sum rules for the spin-dependent structure function G_1(\nu, Q^2) at Q^2=0 and \infty. We generalize these sum rules through studying the virtual-photon…
We investigate the purely non-factorizable $\Lambda_{c}^{+}\to\Xi^{0}K^{+}$ decay using light-cone sum rules. To extract the decay amplitudes, a three-point correlation function is defined and calculated at hadron and quark-gluon level,…
We study instanton corrections to four-point correlation correlation function of half-BPS operators in $\mathcal N=4$ SYM in the light-cone limit when operators become null separated in a sequential manner. We exploit the relation between…
The QCD sum rules for spin-dependent nucleon-nucleon interactions are formulated and their physical implications are studied. The basic object of the study is the correlation function of the nucleon interpolating field, where the matrix…
As an improvement of the QCD sum rule method to study modifications of light vector mesons in nuclear matter and/or at finite temperature, we calculate the Wilson coefficients of all independent gluonic non-scalar operators up to dimension…
Based on a semiclassical expansion for quantum chromodynamics in the instanton liquid background, the correlation function of the $0^{++}$ scalar glueball current is given, and the properties of the $0^{++}$ scalar glueball are studied in…
We apply QCD Finite Energy Sum Rules to the scalar-isoscalar current to determine the lightest $u \bar{u} + d \bar{d}$ meson in this channel. We use `pinch-weights' to improve the reliability of the QCD predictions and reduce the…
The correlator of two gluonic operators plays an important role for example in transport properties of a Quark Gluon Plasma (QGP) or in sum rules for glueballs. In [1] an operator product expansion (OPE) at zero temperature was performed…
We address the nonperturbative structure of topological strings and c=1 matrix models, focusing on understanding the nature of instanton effects alongside with exploring their relation to the large-order behavior of the 1/N expansion. We…
The theory of the `proton spin' effect proposed in our earlier papers is extended to include the chiral SU(3) symmetry breaking and flavour mixing induced by non-vanishing quark masses in QCD. The theoretical basis is the derivation of…
In the instanton ensemble the fermionic zero modes collectivize and break chiral symmetry. Recent studies of resulting zero mode zone confirm its very small width and overall importance for lattice simulations. Confinement however has been…
We propose a new approach to construct QCD sum rules for the pi NN coupling constant, g, starting from the vacuum-to-pion correlation function of the interpolating fields of two nucleons and taking its matrix element with respect to nucleon…
We apply a recently constructed model of analytic QCD in the Operator Product Expansion (OPE) analysis of the tau lepton decay data in the V+A channel. The model has the running coupling A(Q^2) with no unphysical singularities, i.e., it is…
We derive and systematically analyze scalar glueball correlation functions in both the hard-wall and dilaton soft-wall approximations to holographic QCD. The dynamical content of the holographic correlators is uncovered by examining their…
We calculate the leading direct-instanton contributions to the operator product expansion of the nucleon correlator in a magnetic background field and set up improved QCD sum rules for the nucleon magnetic moments. Remarkably, the instanton…
The Operator Product Expansion (OPE) of current correlators at short distances beyond perturbation theory in QCD, together with Cauchy's theorem in the complex energy plane, are the pillars of the method of QCD sum rules. This technique…
Contrary to some previous claims, we find a sizable instanton contribution to the finite energy sum rule used to extract the value of the strong coupling from the measured $\tau$ decay widths. It is of the same order of magnitude as…
We present evidence for unquenching effects in N_f=2, 16^3 32 ensembles by comparing with `equivalent' quenched data at r_0~5.0. A (small) VEV for torelons signals (weak) string breaking. A 15-20 % reduction in the scalar glueball mass…
Accurate non-perturbative calculations of glueballs are performed using light-front quantised SU(N) gauge theory, to leading order of the 1/N expansion. Based on early work of Bardeen and Pearson, disordered gauge-covariant link variables M…