BRST quantization in anti-de Sitter space

We discuss the status of the superstring theory on adS(5) x S-5 space and difficulties with its quantization due to the nonlinear realization of the SU(2, 2\4) superconformal symmetry. We propose a toy model in two dimensions where this symmetry is realized linearly and supertwistors are used as 'quarks' of this supergroup. A possible relation between the string theory and the toy model is studied in the case of a massive particle propagating in AdS(5) space: a generalized twister construction is shown to lead to a quadratic action and simple BRST quantization. We hope that these results will help to also eventually quantize the string on adS(5) x S-5. This paper is based on work done in collaboration with P Claus, M Gunaydin, J Rahmferd and Y Zunger.