Enhanced Symmetries and Tensor Theories in Six Dimensions

Abstract

The partition functions (18) and (21) are constructed from the A k+ 1 , modular invariant Z k \( (\bar \tau ,\tau ) \) and related twisted expressions (22). These correspond to excitations of a type II fundamental string in a background described by degrees of freedom transverse to the NS fivebrane. The incorporation of exact results on Liouville cft may modify which states survive in this theory, and hence their gauge symmetry properties. We note the occurrence of the A k+ 1 modular invariants, and contrast this theory with a type II compactification[7–9] described by a 2D supersymmetric gauge theory leading to a D=6, N=(1,1) theory with massless spectrum of 1 SG multiplet, 19 U(1) and l SU(2) vector supermultiplets. A deeper understanding of how the conventional type IIcft breaks down in this case, due to massless solitons, may guide us to a more economical description of how string theory picks the vacum. It is believed that the appearance of these massless non-perturbative BPS states may be an important mechanism for the way in which nature incorporates gauge symmetry in string theory.