EMBEDDINGS FOR NONCRITICAL SUPERSTRINGS

It was previously shown that at critical central charge, N-extended su perstrings can be embedded in (N+1)-extended superstrings. In other wo rds, (N=0, c=26)-->(N=1, c=15)-->(N=2 c=6)-->(N=3, c=0)-->(N=4, c=0). In this paper, we show that similar embeddings are also possible for N -extended superstrings at non-critical central charge. For any x, the embedding is (N=0, c=26+x)-->(N=1, c= 15+x)-->(N=2, c=6+x)-->(N=3, c=x )-->(N=4, c=x). As was conjectured by Vafa, the (N=2, c= 9)-->(N=3, c= 3) embedding can be used to prove that N=O topological strings are spe cial vaccua of N=1 topological strings.