Non-tachyonic type 0B orientifolds, non-supersymmetric gauge theories and cosmological RG flow

We discuss gauge theories on D3 branes embedded in special non-tachyonic orientifolds of the OB string theory. In general, they correspond to non-supersymmetric SU(N) gauge theories with scalars in the adjoint representation and spinors in the (anti-)symmetric representation. We study these theories via the AdS/CFT correspondence and present evidence of their relation to N = 4 SYM in the planar limit. We also discuss finite N properties, focusing in particular on the renormalization group flow. Up to two loops, the logarithmic running of the gauge coupling is described by the dilaton tadpole and the cosmological constant that naturally emerge on the string theory side. (C) 2000 Elsevier Science B.V. All rights reserved.