On the instanton-induced portion of the nucleon strangeness
  We calculate the instanton contribution to the proton strangeness in the MIT bag enriched by the presence of a dilute instanton liquid. The evaluation is based on expressing the nucleon matrix elements of bilinear strange quark operators in terms of a model valence nucleon state and interactions producing quark-antiquark fluctuations on top of that valence state. Our method combines the usage of the evolution operator containing a strangeness source, and the Feynman-Hellmann theorem. It enables one to evaluate the strangeness in different Lorentz channels in, essentially, the same way. Only the scalar channel is found to be affected by the interaction induced by the random instanton liquid. 
D. Klabucar, K. Kumericki, B. Melic and I. Picek