Calculating fπ in the consistent ladder approximation

We recalculate the pion decay constant ƒ π and the vacuum expectation value 〈 ψψ〉 in a new ladder approximation scheme to the Schwinger-Dyson and Bethe-Salpeter equations which is consistent both with the axial Ward-Takahashi identity and Z 2 = 1 condition (or the vector Ward identity in the abelian case). We find that our previous numerical results remain qualitatively unchanged: in particular, the Pagels-Stokar formula is a good approximation to ƒ π which agrees with the ladder-exact value to within 5%–30%.