NONLINEAR REALIZATIONS OF SUPERCONFORMAL AND W-ALGEBRAS AS EMBEDDINGSOF STRINGS

We propose a simple method for constructing representations of (super) conformal and nonlinear W-type algebras in terms of their subalgebras and corresponding Nambu-Goldstone fields, We apply it to N = 2 and N = 1 superconformal algebras and describe in this way various embeddings of strings and superstrings for which these algebras and their subalg ebras define world-sheet symmetries. Besides reproducing the known exa mples, we present some new ones, in particular an embedding of the bos onic string with additional U(1) affine symmetry into N = 2 superstrin g. We also apply our method to the non-linear W-3((2)) algebra and dem onstrate that the linearization procedure worked out for it some time ago gets a natural interpretation as a kind of string embedding. All t hese embeddings include the critical ones as particular cases. (C) 199 8 Published by Elsevier Science B.V.