Classical geometry and gauge duals for fractional branes on ALE orbifolds

We investigate the classical geometry corresponding to a collection of fractional D3 branes in the orbifold limit C-2/Gamma, of an ALE space. We discuss its interpretation in terms of the world-volume gauge theory on the branes, which is in general a non conformal N = 2 Yang-Mills theory with matter. The twisted fields reproduce the perturbative behaviour of the gauge theory. We regulate the IR singularities for both twisted and untwisted fields by means of an enhancon mechanism qualitatively consistent with the gauge theory expectations. The five-form flux decreases logarithmically towards the IR with a coefficient dictated by the gauge theory beta -functions. (C) 2001 Elsevier Science B.V. All rights reserved.