On possible Chern classes of stable bundles on Calabi–Yau threefolds

Abstract

Supersymmetric heterotic string models, built from a Calabi–Yau threefold X endowed with a stable vector bundle V , usually lead to an anomaly mismatch between c 2 ( V ) and c 2 ( X ) ; this leads to the question whether the difference can be realized by a further bundle in the hidden sector. In [M.R. Douglas, R. Reinbacher, S.-T. Yau, Branes, Bundles and Attractors: Bogomolov and Beyond, math.AG/0604597], a conjecture is stated which gives sufficient conditions on cohomology classes on X to be realized as the Chern classes of a stable reflexive sheaf V ; a weak version of this conjecture predicts the existence of such a V if c 2 ( V ) is of a certain form. In this note, we prove that on elliptically fibered X infinitely many cohomology classes c ∈ H 4 ( X , Z ) exist which are of this form and for each of them a stable S U ( n ) vector bundle with c = c 2 ( V ) exists.