The reasons for using low-lying Dirac eigenmodes to probe the local structure of topological charge fluctuations in QCD are discussed, and the interpretation of the local chiral orientation probability distribution in these modes (as compared with the instanton picture) is clarified. The results with overlap Dirac operator in Wilson gauge backgrounds at lattice spacings ranging from a~0.04 fm to a~0.12 fm are reported, and it is found that the size and density of local structures responsible for double-peaking of the distribution are in disagreement with the assumptions of the Instanton Liquid Model. We argue that our results suggest that vacuum fluctuations do not produce locally quantized (integer-valued) topological charge in QCD, contrary to the semiclassical picture.

Authors: I. Horvath, S.J. Dong, T. Draper, N. Isgur, F.X. Lee, K.F. Liu, J. McCune, H.B. Thacker, J.B. Zhang

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