Homological Algebra of Twisted Quiver Bundles

Several important cases of vector bundles with extra structure(such as Higgs bundles and triples) may be regarded as examplesof twisted representations of a finite quiver in the categoryof sheaves of modules on a variety/manifold/ringed space. Itis shown that the category of such representations is an abeliancategory with enough injectives by the construction of an explicitinjective resolution. Using this explicit resolution, a longexact sequence is found that computes the Ext groups in thisnew category in terms of the Ext groups in the old category.The quiver formulation is directly reflected in the form ofthe long exact sequence. It is also shown that under suitablecircumstances, the Ext groups are isomorphic to certain hypercohomologygroups.