Compact quantum homogeneous Kähler spaces

Abstract

Noncommutative Kähler structures provide an algebraic framework for studying noncommutative complex geometry on quantum homogeneous spaces. In this paper, we introduce the notion of a compact quantum homogeneous Kähler space which gives a natural set of compatibility conditions between covariant Kähler structures and Woronowicz’s theory of compact quantum groups. Each such object admits a Hilbert space completion possessing a remarkably rich yet tractable structure. The analytic behaviour of the associated Dolbeault–Dirac operators is moulded by the complex geometry of the underlying calculus. In particular, twisting the Dolbeault–Dirac operator by a negative Hermitian holomorphic module is shown to give a Fredholm operator if and only if the top anti-holomorphic cohomology group is finite dimensional. In this case, the operator’s index coincides with the twisted holomorphic Euler characteristic of the underlying noncommutative complex structure. The irreducible quantum flag manifolds, endowed with their Heckenberger–Kolb calculi, are presented as motivating examples.