1 research outputs found
Kugo-Ojima confinement criterion, Zwanziger-Gribov horizon condition, and infrared critical exponents in Landau gauge QCD
The Kugo-Ojima confinement criterion and its relation to the infrared
behaviour of the gluon and ghost propagators in Landau gauge QCD are reviewed.
The realization of this confinement criterion (which in Landau gauge relates to
Zwanziger's horizon condition) results from quite general properties of the
ghost Dyson-Schwinger equation. The numerical solutions for the gluon and ghost
propagators obtained from a truncated set of Dyson-Schwinger equations provide
an explicit example for the anticipated infrared behaviour. These results are
in good agreement, also quantitatively, with corresponding lattice data
obtained recently. The resulting running coupling approaches a fixed point in
the infrared, . Solutions for the coupled system of
Dyson-Schwinger equations for the quark, gluon and ghost propagators are
presented. Dynamical generation of quark masses and thus spontaneous breaking
of chiral symmetry is found. In the quenched approximation the quark propagator
functions agree well with those of corresponding lattice calculations. For a
small number of light flavours the quark, gluon and ghost propagators deviate
only slightly from the quenched ones. While the positivity violation of the
gluon spectral function is apparent in the gluon propagator, there are no clear
indications of positivity violations in the Landau gauge quark propagator.Comment: 10 pages, 4 figures; invited talk presented by R. Alkofer at the
International Conference Confinement V Gargnano, Italy, September 10-14, 200