  We characterize the integral cohomology and the rational homotopy type of the
maximal Borel-equivariantization of the combined Hopf/twistor fibration, and
find that subtle relations satisfied by the cohomology generators are just
those that govern Horava-Witten's proposal for the extension of the
Green-Schwarz mechanism from heterotic string theory to heterotic M-theory. We
discuss how this squares with the Hypothesis H that the elusive mathematical
foundation of M-theory is based on charge quantization in J-twisted Cohomotopy
theory.
