News on Disconnected Diagrams

Abstract

We present evidence for disconnected contributions to the $\sigma_{\pi N}$ term and the flavor singlet axial coupling $g_A^0$ of the proton on full QCD configurations, which are obtained by means of improved stochastic estimator techniques. Furthermore we discuss results from the fermionic determination of the topological charge of the QCD vacuum (in the spirit of the Athiya-Singer theorem) again achieved with stochastic estimator methods. It turns out that this approach provides an monitor for the tunneling efficiency of the HMC on QCD with dynamical Wilson fermions which is independent on the pure gluonic method that implies cooling.