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Roles of the quark field in the infrared lattice Coulomb gauge and Landau gauge QCD

Presenter: Sadataka Furui — Teikyo University

Sadataka Furui, Hideo Nakajima

We gauge fixed unquenched configurations of the MILC collaboration [1] which contain Nf=2 and 3 Kogut-Susskind (KS) fermions and those of the QCDOC collaboration [2] which contain Nf=2+1 domain-wall fermioins (DWF) to the Coulomb gauge and measured the gluon propagator, the ghost propagator, the running coupling, the color Coulomb potential and the Coulomb form factor.

The running coupling αCoul(q→2) measured from the color-Coulomb potential multiplied by q→2 of the DWF configurations and the KS fermion configurations agree within errors. The gluon propagator of the DWF configurations at zero momentum is strongly suppressed, while that of the KS fermion is infrared finite. Consequently the running coupling αI(q→2)[3] measured from the gluon dressing function and the ghost dressing function of the DWF is smaller than that of the KS fermion.

These data were compared with those of Landau gauge, in which the gluon propagators are found to be infrared finite. We observed that the Kugo-Ojima confinement parameter also depends on the presence or absence of the dynamical fermions[4]. These dependences on the fermions urge a reconsideration of the quark field subdominance scenario of the Dyson-Schwinger approach in the infrared QCD[5].

References: [1] C. Bernard et al., Phys. Rev. D 54 4585(1996); Phys. Rev. D 64 054506 (2001). [2] C. Allton et al., hep-lat/0701013 [3] C.S. Fischer and D. Zwanziger, Phys. Rev. D 72,054005 (2005). [4] S. Furui and H. Nakajima, Braz. J. Phys.37,186-192 (2007); hep-lat/0612009. [5] C.S. Fischer and R. Alkofer, Phys. Rev. D 67, 094020 (2003).