Twists and Wilson loops in the string theory of two-dimensional QCD

Abstract

The string theory that describes two-dimensional QCD in an asymptotic 1/ N expansion is investigated further. A complete geometrical description of the QCD partition function on an arbitrary manifold is given in terms of maps from a two-dimensional orientable surface onto the target space. This includes correction terms that arise on surfaces with genus G ≠ 1, which are described geometrically by the insertion of extra “twist” points in the covering maps. In addition, the formalism is derived for calculating the vacuum expectation value of an arbitrary product of Wilson loops on an arbitrary two-dimensional manifold in terms of maps from an open string world sheet onto the target space.