AdS/CFT duality for string orbifolds

Abstract

In this thesis we discuss orbifolds of type IIB string theory on AdS_5 x S^5 and their dual field theories. These models can be studied by taking exactly solvable limits and with integrability techniques. We discuss these techniques and apply them to two Z_2-orbifolds.

We first study a half-supersymmetric orbifold space which keeps an AdS_5 x S^1 subspace fixed. The orbifolding procedure introduces a twisted sector localised on this fixed set. The preserved supersymmetry allows us to use localisation results to study twisted sector correlation functions and expand them at strong coupling. We present a strategy to match these strong-coupling corrections to alpha'^3-corrections of the supergravity action. This requires a resolution of the orbifold singularity. We then identify additional supergravity modes localised on the resolution as the twisted sector and study their effective action.

The second orbifold we consider breaks all supersymmetry and leads to type 0B string theory on AdS_5 x S^5. Although we cannot rely on supersymmetry in this case, integrability is preserved and allows us to study the twisted sector. The twisted sector groundstate is a tachyon in flat space, but gets partially stabilised when background flux is turned on. We employ integrability to study the conformal dimension of the dual operator and find an imaginary anomalous dimension for an operator O_{-2} of R-charge 2. We discuss a possible connection to the breakdown of conformal symmetry induced by the double-trace operator O_{-2}O_{-2}.