  The light pseudoscalar mesons play a twofold role: they may or have to be
regarded both as low-lying bound states of the fundamental degrees of freedom
of quantum chromodynamics as well as the (pseudo-) Goldstone bosons of the
spontaneously broken chiral symmetries of quantum chromodynamics. We
interrelate these aspects in a single quantum-field-theoretic approach relying
on the Bethe-Salpeter formalism in instantaneous approximation by very simple
means: the shape of the pseudoscalar-meson Bethe-Salpeter wave function
dictated by chiral symmetry is used in Bethe-Salpeter equations for bound
states of vanishing mass, in order to deduce analytically the interactions
which govern the bound states under study. In this way, we obtain exact
Bethe-Salpeter solutions for pseudoscalar mesons, in the sense of establishing
the rigorous relationship between, on the one hand, the relevant interactions
and, on the other hand, the Bethe-Salpeter amplitudes that characterize the
bound states.
