Existence and uniqueness of advanced and retarded fundamental solutions
(Green's functions) and of global solutions to the Cauchy problem is proved for
a general class of first order linear differential operators on vector bundles
over globally hyperbolic Lorentzian manifolds. This is a core ingredient to
CAR-/CCR-algebraic constructions of quantum field theories on curved
spacetimes, particularly for higher spin field equations.Comment: revised version: typos; reordering of sec 2; results unchange