Brane Partons and Singleton Strings

We examine p-branes in AdS_D in two limits where they exhibit partonic behavior: rotating branes with energy concentrated to cusp-like solitons; tensionless branes with energy distributed over singletonic bits on the Dirac hypercone. Evidence for a smooth transition from cusps to bits are found. First, each cusp yields D-2 normal-coordinate bound states with protected frequencies; and is dual to a short open p-brane becoming massless on the giant-vacuum brane at the end-of-the-universe. Second, the N_{bit}-sector is an sp(2N_{bit})-gauged phase-space sigma model giving rise to symmetrized N_{bit}-pletons of the minimal higher-spin algebra ho_0(D-1,2)\supset so(D-1,2). The continuum limit leads to a 2d chiral sp(2)-gauged sigma model which is critical in D=7; equivalent 'a la Bars-Vasiliev to an su(2)-gauged spinor string; and furthermore dual to WZW model in turn containing a topological \hat{so}(6,2)_{-2}/(\hat{so}(6)\oplus\hat{so}(2))_{-2} coset model giving rise to a chiral ring generated by singleton-valued weight-0 spin fields. Moreover, the two-bit truncation leads via a reformulation 'a la Cattaneo-Felder-Kontsevich to a topological open string on the phase space of the D-dimensional Dirac hypercone giving rise to the Vasiliev equations based on vector oscillators and weak sp(2)-projection. Geometrically, the bi-locality reflects broken boundary-singleton worldlines, and the intertwiner kappa relates T and R-ordered deformations of the boundary and the bulk of th