Quantum Algebras Associated to Irreducible Generalized Flag Manifolds

Abstract

The first part of this thesis deals with certain properties of the quantum symmetric and exterior algebras of Type 1 representations of $U_q(g)$ defined by Berenstein and Zwicknagl. We define a notion of a commutative algebra object in a coboundary category, and we prove that the quantum symmetric algebra of a module is the universal commutative algebra generated by that module. That is, the functor assigning to a module its quantum symmetric algebra is left adjoint to a forgetful functor. We also prove a conjecture of Berenstein and Zwicknagl, stating that the quantum symmetric and exterior cubes exhibit the same amount of "collapsing" relative to their classical counterparts. We prove that those quantum exterior algebras that are flat deformations of their classical analogues are Frobenius algebras. We also develop a rigorous framework for discussing continuity and limits of the structures involved as the deformation parameter q varies along the positive real line. The second part deals with quantum analogues of Clifford algebras and their application to the noncommutative geometry of certain quantum homogeneous spaces. We introduce the quantum Clifford algebra through its spinor representation via creation and annihilation operators on one of the flat quantum exterior algebras discussed in the first part. The proof that the spinor representation is irreducible relies on the Frobenius property discussed previously. We use this quantum Clifford algebra to revisit Krahmer's construction of a Dolbeault-Dirac-type operator on a quantized irreducible flag manifold. This operator is of the form $d+d^*$, and we relate $d$ to the boundary operator for the Koszul complex of a certain quantum symmetric algebra, which shows that $d^2=0$. This is a first step toward a Parthasarathy-type formula for the spectrum of the square of the Dirac operator.