We develop a graded version of the theory of cyclotomic q-Schur algebras, in
the spirit of the work of Brundan-Kleshchev on Hecke algebras and of Ariki on
q-Schur algebras. As an application, we identify the coefficients of the
canonical basis on a higher level Fock space with q-analogues of the
decomposition numbers of cyclotomic q-Schur algebras.
We construct knot invariants categorifying the quantum knot variants for all
representations of quantum groups. We show that these invariants coincide with
previous invariants defined by Khovanov for sl_2 and sl_3 and by
Mazorchuk-Stroppel and Sussan for sl_n. We also suggest an approach to showing
that these knot homologies are functorial. Our technique uses categorifications
of the tensor products of integrable representations of Kac-Moody algebras and
quantum groups, constructed a prequel to this paper.
We construct knot invariants categorifying the quantum knot variants for all
representations of quantum groups. We show that these invariants coincide with
previous invariants defined by Khovanov for sl(2) and sl(3) and by
Mazorchuk-Stroppel and Sussan for sl(n). We also suggest an approach to showing
that these knot homologies are functorial.
We give a geometric interpretation of the Jones-Ocneanu trace on the Hecke
algebra, using the equivariant cohomology of sheaves on SL(n). This
construction makes sense for all simple groups, so we obtain a generalization
of the Jones-Ocneanu trace to Hecke algebras of other types. We show that this
trace coincides with a trace defined by Gomi using Lusztig's Fourier transform,
and give a short geometric proof of Gomi's expansion of this trace in terms of
characters.
We show that each integral block of parabolic category O (including singular
ones) for a semi-simple Lie group can be realized as a full subcategory of a
``thick'' category O over a finite W-algebra for the same Lie group.
The nilpotent used to construct this finite W-algebra is determined by the
central character of the block, and the subcategory taken is that killed by a
two-sided ideal depending on the original parabolic. The equivalences in
question are induced by those of Milicic-Soergel and Skryabin.