A Jantzen type filtration for generalised Varma modules of Lie superalgebras
is introduced. In the case of type I Lie superalgebras, it is shown that the
generalised Jantzen filtration for any Kac module is the unique Loewy
filtration, and the decomposition numbers of the layers of the filtration are
determined by the coefficients of inverse Kazhdan-Lusztig polynomials.
Furthermore, the length of the Jantzen filtration for any Kac module is
determined explicitly in terms of the degree of atypicality of the highest
weight.
Let $\Uq$ be a quantum group. Regarding a (noncommutative) space with
$\Uq$-symmetry as a $\Uq$-module algebra $A$, we may think of equivariant
vector bundles on $A$ as projective $A$-modules with compatible $\Uq$-action.
We construct an equivariant K-theory of such quantum vector bundles using
Quillen's exact categories, and provide means for its compution. The
equivariant K-groups of quantum homogeneous spaces and quantum symmetric
algebras of classical type are computed.