On Hpp-wave/cft 2 Holography *

We briefly review the AdS3/CFT2 correspondence and the holographic issues that arise in the Penrose limit. Exploiting current algebra techniques, developped by D’Appollonio and Kiritsis for the closely related Nappi-Witten model, we obtain preliminary results for bosonic string amplitudes in the resulting Hpp-wave background and comment on how to extend them to the superstring. The AdS3/CFT2 holographic correspondence relates superstring theory onAdS3× S ×M to a two-dimensional superconformal field theory defined as the non-linear σ-model whose target space is the symmetric orbifold M/SN [1, 2, 3]. The four dimensional compactification manifold, M, is chosen to be T 4 or K3. AdS3 × S × M can be thought of as the near horizon geometry of a D1-D5 brane configuration with non-vanishing R-R 3-form flux. Since it is not fully known how to quantize the superstring in the presence of generic R-R backgrounds, it is convenient to consider the S-dual configuration which is supported by a NS-NS 3-form flux [3]. The metric of the resulting F1-NS5 bound state is ds = f 1 (−dx0 + dx1 ) + f5 ( dr + rdΩ3 ) + dsM ∗Based on the talk given at the ‘Tenth Marcel Grossmann Meeting’, 20-26 July 2003, CBPFICRA, Rio de Janeiro, Brazil. At present, the Pure Spinor formalism is the most promising approach to tackle this outstanding problem [5].