Topological Structure of the QCD Vacuum Revealed by Overlap Fermions

Abstract

Overlap fermions preserve a remnant of chiral symmetry on the lattice. They are a powerful tool to investigate the topological structure of the vacuum of Yang-Mills theory and full QCD. Recent results concerning the localization of topological charge and the localization and local chirality of the overlap eigenmodes are reported. The charge distribution is radically different, if a spectral cut-off for the Dirac eigenmodes is applied. The density q(x) is changing from the scale-a charge density (with full lattice resolution) to the ultraviolet filtered charge density. The scale-a density, computed on the Linux cluster of LRZ, has a singular, sign-coherent global structure of co-dimension 1 first described by the Kentucky group. We stress, however, the cluster properties of the UV filtered topological density resembling the instanton picture. The spectral cut-off can be mapped to a bosonic smearing procedure. The UV filtered field strength reveals a high degree of (anti)selfduality at "hot spots" of the action. The fermionic eigenmodes show a high degree of local chirality. The lowest modes are seen to be localized in low-dimensional space-time regions.Comment: 13 pages, 11 figures, accepted to appear in the Proceedings of "HLRB, KONWIHR and Linux-Cluster: Review, Results and Future Projects Workshop", Leibniz Rechenzentrum Munich, December 200

Chiral superfluidity of the quark–gluon plasma

“…In Refs. [22][23][24][25][26][27] it has been discovered and confirmed by [28,29] that topological charge density forms long-range coherent global structures around a locally one-dimensional network of strong fields (so-called "skeleton"). Though the simulations were performed for low temperatures, the skeletons could very well survive slightly above the deconfinement transition, since there is a corresponding long-range order of gluonic fields [30] in the case of nonvanishing topological susceptibility.…”