Quasicoherent sheaves on complex noncommutative two-tori

TL;DR

This paper introduces quasicoherent sheaves on complex noncommutative two-tori, establishing their derived category equivalence with elliptic curves and classifying projective objects by rank.

Contribution

It extends the theory of quasicoherent sheaves to noncommutative tori, defines a real-valued rank, and classifies projective objects in a quotient category.

Findings

Derived category of quasicoherent sheaves on T is equivalent to that on an elliptic curve.

Projective objects of finite rank are classified by their rank.

Finite rank objects form a category equivalent to finitely presented modules over a semihereditary algebra.

Abstract

We introduce the notion of a quasicoherent sheaf on a complex noncommutative two-torus $T$ as an ind-object in the category of holomorphic vector bundles on $T$. Extending the results of math.QA/0211262 and math.QA/0308136 we prove that the derived category of quasicoherent sheaves on $T$ is equivalent to the derived category of usual quasicoherent sheaves on the corresponding elliptic curve. We define the rank of a quasicoherent sheaf that can take arbitrary nonnegative real values. We study the category $\Qcoh(\eta_T)$ obtained by taking the quotient of the category of quasicoherent sheaves by the subcategory of objects of rank zero (called torsion sheaves). We show that projective objects of finite rank in $\Qcoh(\eta_T)$ are classified up to an isomorphism by their rank. We also prove that the subcategory of objects of finite rank in $\Qcoh(\eta_T)$ is equivalent to the category of finitely presented modules over a semihereditary algebra.