K-K excitations on AdS_5 x S^5 as N=4 ``primary'' superfields

TL;DR

The paper addresses the KK spectrum of type IIB string theory on AdS5×S5 within the AdS/CFT framework. It proposes that the entire tower of KK excitations is captured by twisted chiral N=4 superfields, constructed as SU(n) singlet polynomials of the boundary singleton in harmonic superspace. The p-th order polynomial yields a short KK multiplet with degeneracy $256 × (p^2(p^2−1)/12)$ and includes the massless graviton multiplet at p=2; lower p cases are special. The authors extend the analysis to theories with less supersymmetry and relate the structure to holomorphic boundary correlators of AdS amplitudes, underscoring a concrete connection between bulk KK physics and boundary CFT data.

Abstract

We show that the K-K spectrum of IIB string on AdS_5 x S_5 is described by ``twisted chiral'' N=4 superfields, naturally described in ``harmonic superspace'', obtained by taking suitable gauge singlets polynomials of the D3-brane boundary SU(n) superconformal field theory. To each p-order polynomial is associated a massive K-K short representation with 256 x 1/12 p^2(p^2 -1) states. The p=2 quadratic polynomial corresponds to the ``supercurrent multiplet'' describing the ``massless'' bulk graviton multiplet.