  We define a canonical basis of the $q$-deformed Fock space representation of
the affine Lie algebra $\glchap_n$. We conjecture that the entries of the
transition matrix between this basis and the natural basis of the Fock space
are $q$-analogues of decomposition numbers of the $v$-Schur algebras for $v$
specialized to a $n$th root of unity.
