**Research Interests**
My research concerns string theory. At present I am interested in finding an explicit expression for the n-loop superstring amplitude and proving that it is finite. My field of research is particle theory, more specifically string theory. I am also interested in the recent results of Seiberg and Witten in supersymmetric field theories.
**Current Projects**
My present research concerns the problem of topology changing in string theory. It is currently believed that one has to sum over all string backgrounds and all topologies in doing the functional integral. I suspect that certain singular string backgrounds may be equivalent to topology changes, and that it is consequently only necessary to sum over string backgrounds. As a start I am investigating topology changes in two-dimensional target spaces. I am also interested in Seiberg-Witten invariants. Although much has been learned, some basic questions remain, and I hope to be able at least to understand the simpler of these questions.
** Selected Publications**
S. Mandelstam, “Light-cone superspace and the finiteness of the N = 4 model,” in *Problems in Unification and Supergravity*, AIP Conference Proceedings, No. 116 (1983).
S. Mandelstam, “The interacting-string picture and functional integration,” in *Unified String Theories*, Proceedings of the Workshop held at the I.T.P., Santa Barbara, August 1985, World Scientific, Singapore, Vol. **46** (1986).
S. Mandelstam, “The n-loop string amplitude,” in *Frontiers of High-Energy Physics*, Lectures given at the 7th U.K. Institute for Theoretical High-Energy Physicists, Imperial College, London, 17 August - 6 September 1986, Adam Hilger, Bristol, pp. 1-34 (1987).
S. Mandelstam, “The n-loop string amplitude. Explicit formulas, finiteness and absence of ambiguities,” *Phys. Lett. ***B277**, 82 (1992). |