Classical geometry and gauge duals for fractional branes on ALE orbifolds

We investigate the classical geometry corresponding to a collection of frac tional D3 branes in the orbifold limit C-2/Gamma, of an ALE space. We discu ss its interpretation in terms of the world-volume gauge theory on the bran es, which is in general a non conformal N = 2 Yang-Mills theory with matter . The twisted fields reproduce the perturbative behaviour of the gauge theo ry. We regulate the IR singularities for both twisted and untwisted fields by means of an enhancon mechanism qualitatively consistent with the gauge t heory expectations. The five-form flux decreases logarithmically towards th e IR with a coefficient dictated by the gauge theory beta -functions. (C) 2 001 Elsevier Science B.V. All rights reserved.