Infrared Properties of QCD from Dyson-Schwinger equations

I review recent results on the infrared properties of QCD from Dyson-Schwinger equations. The topics include infrared exponents of one-particle irreducible Green's functions, the fixed point behaviour of the running coupling at zero momentum, the pattern of dynamical quark mass generation and properties of light mesons.Comment: 47 pages, 19 figures, Topical Review to be published in J.Phys.G, v2: typos corrected and some references adde

A dynamical {eta}{prime} - mass from an infrared enhanced gluon exchange

The pseudo-scalar flavor-singlet meson mixes with two gluons. A dimensional argument by Kogut and Susskind shows that this can screen the Goldstone pole of the chiral limit in this channel, if the gluon correlations are infrared enhanced. Using a gluon propagator as singular as {sigma}/k{sup 4} for k{sup 2} {yields} 0 we relate the screening mass to the string tension {sigma}. In the Written-Veneziano action to describe the {eta}-{eta}{prime} mixing this relation yields masses of about 810MeV for the {eta}{prime}, 430MeV for the {eta} and a mixing angle of about -30{degrees} from the phenomenological value {sigma} {approx} 0.18GeV{sup 2}. The very weak temperature dependence of the string tension should make this mechanism experimentally distinguishable from exponentially temperature dependent instanton model predictions