The Curtis conjecture asserts that the positive-degree image of the stable mod-two Hurewicz homomorphism
is spanned by the Hopf invariant one classes and the Kervaire invariant one classes that exist. Here
is the basepoint component of the infinite loop space of the sphere
spectrum. The Hopf classes are
,
, and
, in stems 1, 3, and 7. The Kervaire classes
, when they exist, have stem
.