Quiver Schur algebras for linear quivers

Abstract

We define a graded quasi-hereditary covering for the cyclotomic quiver Hecke algebras $\mathcal{R}^Λ_n$ of type $A$ when $e=0$ (the linear quiver) or $e\ge n$. We show that these algebras are quasi-hereditary graded cellular algebras by giving explicit homogeneous bases for them. When $e=0$ we show that the KLR grading on the quiver Hecke algebras is compatible with the gradings on parabolic category $\mathcal{O}$ previously introduced in the works of Beilinson, Ginzburg and Soergel and Backelin. As a consequence, we show that when $e=0$ our graded Schur algebras are Koszul over field of characteristic zero. Finally, we give an LLT-like algorithm for computing the graded decomposition numbers of the quiver Schur algebras in characteristic zero when $e=0$.

Major revision to improve readability. We have added a proof that our quiver Schur algebras are graded Morita equivalent to those of Stroppel-Webster. This result is then used to match up the KLR and category O gradings in the degenerate case. Explicit formulas for the inverse parabolic Kazhdan-Lusztig polynomials are also given