Supersymmetry of Tensionless Rotating Strings in AdS_5 x S^5, and Nearly-BPS Operators

TL;DR

The paper analyzes a class of rotating strings in AdS5×S5 with SO(6) angular momenta, showing that in the large-J,J' limit these strings become effectively tensionless and preserve a fraction of supersymmetry. Using κ-symmetry, it is shown that tensionless strings generically preserve 1/8 of the background supersymmetries, with enhancements to 1/4 or 1/2 in special cases (J=0 or J'=0). A BPS bound derived from the PSU(2,2|4) superalgebra implies E ≥ |J| + 2|J'|, which is saturated in the large-J limit, signaling near-supersymmetric behavior. The dual CFT operators are identified as nearly-BPS single-trace operators in N=4 SYM, whose anomalous dimensions agree with string energies in the planar, large-J regime, connecting semiclassical string theory to perturbative gauge theory. The work suggests the AdS/CFT tests extend into a nearly-BPS sector and discusses implications for giant gravitons and the free-theory limit.

Abstract

It is shown that a class of rotating strings in AdS_5 x S^5 with SO(6) angular momenta (J,J',J') preserve 1/8-supersymmetry for large J,J', in which limit they are effectively tensionless; when J=0, supersymmetry is enhanced to 1/4. These results imply that recent checks of the AdS/CFT correspondence actually test a nearly-BPS sector.