S-duality, noncritical open string and noncommutative gauge theory

We examine several aspects of S-duality of four-dimensional noncommutative gauge theory. By making duality transformation explicit, we find that S-dual of noncommutative gauge theory is defined in terms of dual noncommutative deformation. In 'magnetic' noncommutative U(1)gauge theory, we show that, in addition to gauge bosons, open D-strings constitute important low-energy excitations: noncritical open D-strings. Upon S-duality, they are mapped to noncritical open F-strings. We propose that, in dual 'electric' noncommutative U(1) gauge theory, the letters are identified with gauge-invariant, open Wilson lines. We argue that the open Wilson lines are chiral due to underlying parity noninvariance and obey spacetime uncertainty relation. We finally argue that, at high energy-momentum limit, the 'electric' noncommutative gauge theory describes correctly dynamics of dclocalized multiple F-strings. (C) 2001 Published by Elsevier Science B.V.