Instanton moduli and brane creation

We obtain new intersecting 5-brane, string and pp-wave solutions in the het erotic string on a torus and on a K3 manifold. In the former case the 5-bra ne is supported by Yang-Mills instantons, and in the latter case both the 5 -brane and the string are supported by the instantons. The instanton moduli are parameterised by the sizes and locations of the instantons. We exhibit two kinds of phase transition in which, for suitable choices of the instan ton moduli, a 5-brane and/or a string can be created. One kind of phase tra nsition occurs when the size of an instanton vanishes, while the other occu rs when a pair of Yang-Mills instantons coalesce. We also study the associa ted five-dimensional black holes and the implications of these phase transi tions for the black-hole entropy. Specifically, we find that the entropy of the three-charge black holes is zero when the instantons are separated and of non-zero scale size, but becomes non-zero (which can be counted microsc opically) after either of the phase transitions. (C) 2000 Elsevier Science B.V. All rights reserved.