  Dynamical chiral symmetry breaking is a nonperturbative phenomenon that may
be studied using QCD's gap equation. Model-independent results can be obtained
with a nonperturbative and symmetry preserving truncation. The gap equation
yields the massive dressed-quark propagator, which has a spectral
representation when considered as a function of the current-quark mass. This
enables an explication of the connection between the infrared limit of the QCD
Dirac operator's spectrum and the quark condensate appearing in the operator
product expansion.

Nuclear Theory;High Energy Physics - Lattice;High Energy Physics - Phenomenology