Gauge covariance of the gap equation: from the rainbow truncation to gauge symmetry constraints

Abstract

The gauge covariance of the quark gap equation is compared for three quark-gluon vertices: the bare vertex, a Ball-Chiu like vertex constrained by the corresponding Slavnov-Taylor identity, and a full vertex including the transverse components derived from transverse Slavnov-Taylor identities. The covariance properties are verified with the chiral quark condensate and the pion decay constant in the chiral limit.

Comments: Invited contribution to the special edition "Chiral Symmetry, and Restoration in Nuclear Dense Matter" to appear in Symmetry. 12 pages and 5 figures, improved discussion of vertex form factor on page 5