The extraction of gA from finite volume systems:: the long and short of it

Due to a pion-pole contribution, the nucleon axial current matrix elements can be visualized in position space as becoming delocalized as the chiral limit is approached, with one-third of the current at distance of order 1/m(pi). However, this delocalization effect will not cause calculations Of g(A) in a finite system with standard boundary conditions (periodic for boson fields, antiperiodic for fermions) to have large finite volume effects. This is seen by calculating g(A) using a nonstandard current with axial quantum numbers. The matrix elements of this new current lacks a pion pole and is not delocalized however, its zero-momentum matrix element is identical to that of the standard axial current both for infinite and finite volumes. (C) 2002 Elsevier Science B.V. All rights reserved.