出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The evidence for the target space duality symmetry associated with massive excited states of closed bosonic string is presented. The vertex operators for excited masive levels of closed bosonic string are constructed for the case where d-dimensions are compactified on a torus. The existence of T-duality is verified for a few massive levels. A systematic procedure is presented to study T-duality symmetry of vertex operators of massive levels of closed bosonic string. It is argued that all vertex operators corresponding to excited massive states can be cast in an O(d;d) invariant form, d being the number of compact dimensions .
