Notes on D-instanton correction to AdS(5) X S-5 geometry

We show that the D-instanton in the AdS(5) X S-5 background is a wormhole c onnecting the background AdS(5) X S-5 to the flat space R-10 located at the position of the D-instanton. By a SL(2,R) rotation of type IIB theory, we can make the global geometry flat in string frame. We also find that, due t o the tight relation between the dilaton and the axion, there is no SL(2,R) element that rakes strong string coupling to weak one without making the a xion ill defined. We also discuss the D-instanton gases. A subtlety on the D-instanton at the boundary or at the horizon is discussed. (C) 1998 Publis hed by Elsevier Science B.V. All rights reserved.