Operator product expansions are applied to dilaton-axion four-point functions. In the expansions of the bilocal fields <()over tilde><()over tilde>, (C) over tilde(C) over tilde and <()over tilde>(C) over tilde, the conformal fields which are symmetric traceless tensors of rank l and have dimensions delta = 2 +l or 8 + l + eta (l) and eta (l) = O(N-2) are identified. The unidentified fields have dimension delta = lambda + l + n(l) with lambda greater than or equal to 10. The anomalous dimensions eta (l) are calculated at order O(N-2) for both 2(-1/2)<()over tilde><()over tilde> + (C) over tilde(C) over tilde) and 2(-1/2)<()over tilde>(C) over tilde + (C) over tilde<()over tilde>) and are found to be the same, proving U(1)y symmetry. The relevant coupling constants are given at order O(1). (C) 2001 Elsevier Science B.V. All rights reserved. [References: 19]
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