  The reduction of the E8 gauge theory to ten dimensions leads to a loop group,
which in relation to twisted K-theory has a Dixmier-Douady class identified
with the Neveu-Schwarz H-field. We give an interpretation of the degree two
part of the eta-form by comparing the adiabatic limit of the eta invariant with
the one loop term in type IIA. More generally, starting with a G-bundle, the
comparison for manifolds with String structure identifies G with E8 and the
representation as the adjoint, due to an interesting appearance of the dual
Coxeter number. This makes possible a description in terms of a generalized WZW
model at the critical level. We also discuss the relation to the index gerbe,
the possibility of obtaining such bundles from loop space, and the symmetry
breaking to finite-dimensional bundles. We discuss the implications of this and
we give several proposals.
