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-dua l 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 t o noncritical open F-strings. We propose that, in dual 'electric' noncommut ative U(1) gauge theory, the letters are identified with gauge-invariant, o pen Wilson lines. We argue that the open Wilson lines are chiral due to und erlying parity noninvariance and obey spacetime uncertainty relation. We fi nally argue that, at high energy-momentum limit, the 'electric' noncommutat ive gauge theory describes correctly dynamics of dclocalized multiple F-str ings. (C) 2001 Published by Elsevier Science B.V.