Type IIB superstring action in AdS_5 x S^5 background

TL;DR

The paper constructs a covariant, κ-symmetric Type IIB superstring action on the AdS5 × S^5 background by formulating a 2d σ-model on the coset SU(2,2|4)/SO(4,1)×SO(5) and deriving a unique action fixed by κ-symmetry. It expresses the action in terms of Cartan 1-forms, decomposes it into a kinetic term and a Wess–Zumino term, and fixes the WZ coefficient to ensure κ-invariance, with the flat-space GS action recovered in the infinite-radius limit. The explicit 2d form is obtained through a θ-expansion, yielding a covariantized flat GS-like term plus θ^4 corrections, along with RR-background couplings encoded in a generalized spinor covariant derivative. The work argues for an exact worldsheet conformal field theory under SU(2,2|4) symmetry, outlines the impact on the string spectrum and vertex operators, and suggests extensions to other AdS backgrounds, establishing a concrete framework for studying IIB strings in AdS5×S^5.

Abstract

We construct the covariant kappa-symmetric superstring action for a type IIB superstring on AdS_5 x S^5 background. The action is defined as a 2d sigma-model on the coset superspace SU(2,2|4) / SO(4,1) x SO(5) and is shown to be the unique one that has the correct bosonic and flat space limits.