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Paper IPM / Physic / 6681  


Abstract:  
We study, using ADHM construction, instanton effects in an \CN=2 superconformal Sp(N) gauge theory, arising as effective field theory on a system of N D3branes near an orientifold 7plane and 8 D7branes in type I' string theory. We work out the measure for the collective coordinates of multiinstantons in the gauge theory and compare with the measure for the collective coordinates of (−1)branes in the presence of 3 and 7branes in type I' theory. We analyse the largeN limit of the measure and find that it admits two classes of saddle points: In the first class the space of collective coordinates has the geometry of AdS_{5}×S^{3} which on the string theory side has the interpretation of the Dinstantons being stuck on the 7branes and therefore the resulting moduli space being AdS_{5}×S^{3}, In the second class the geometry is AdS_{5}×S^{5}/Z_{2} and on the string theory side it means that the Dinstantons are free to move in the 10dimensional bulk. We discuss in detail a correlator of four O(8) flavour currents on the YangMills side, which receives contributions from the first type of saddle points only, and show that it matches with the correlator obtained from F^{4} coupling on the string theory side, which receives contribution from Dinstantons, in perfect accord with the AdS/CFT correspondence. In particular we observe that the sectors with odd number of instantons give contribution to an O(8)odd invariant coupling, thereby breaking O(8) down to SO(8) in type I' string theory. We finally discuss correlators related to R^{4}, which receive contributions from both saddle points.
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