Fractional branes and N=1 gauge theories

We discuss fractional D3-branes on the orbifold C-3/Z(2) x Z(2). We study the open and the closed string spectrum on this orbifold. The corresponding N = 1 theory on the brane has, generically, a U(N-1) x U(N-2) x U(N-3) x U(N-4) gauge group with matter in the bifundamental. In particular, when only one type of brane is present, one obtains pure N = 1 Yang-Mills. We study the coupling of the branes to the bulk fields and present the corresponding supergravity solution, valid at large distances. By using a probe analysis, we are able to obtain the Wilsonian-function for those gauge theories that possess some chiral multiplet. Although, due to the lack of moduli, the probe technique is not directly applicable to the case of pure V = I Yang-Mills, we point out that the same formula gives the correct result also for this case.