  Let R be a commutative noetherian local ring with completion R^. We apply
differential graded (DG) algebra techniques to study descent of modules and
complexes from R^ to R' where R' is either the henselization of R or a pointed
\'etale neighborhood of R: We extend a given R^-complex to a DG module over a
Koszul complex; we describe this DG module equationally and apply Artin
approximation to descend it to R.
  This descent result for Koszul extensions has several applications. When R is
excellent, we use it to descend the dualizing complex from R^ to a pointed
\'etale neighborhood of R; this yields a new version of P. Roberts' theorem on
uniform annihilation of homology modules of perfect complexes. As another
application we prove that the Auslander Condition on uniform vanishing of
cohomology ascends to R^ when R is excellent, henselian, and Cohen--Macaulay.
