Hidden extended superconformal symmetries in superstrings

Abstract
We study hidden extended superconformal symmetries in superstring theories. It is shown that N=1 and 2 locally supersymmetric strings actually possess N=2 and 4 extended global superconformal symmetries, respectively. We also discuss how these hidden larger symmetries on the world sheet give rise to the spacetime supersymmetries and construct the supercharges using only symmetry generators on the world sheet.