Scale invariant low-energy effective action in N=3 SYM theory

Using the harmonic superspace approach we study the problem of low-energy effective action in N = 3 SYM theory. The candidate effective action is a scale and gamma(5)-invariant functional in full N = 3 superspace built out of M = 3 off-shell superfield strengths. This action is constructed as N= 3 super-field generalization of F-4/phi(4) component term which is leading in the low-energy effective action and is simultaneously the first nontrivial term in scale invariant Born-Infeld action. All higher-order terms in the scale invariant Born-Infeld action are also shown to admit an off-shell superfield completion in N = 3 harmonic superspace. (C) 2004 Elsevier B.V. All rights reserved.