  We demonstrate in examples that the covariant retarded Green's functions in
electromagnetism and linearized gravity work as expected in de Sitter
spacetime. We first clarify how retarded Green's functions should be used in
spacetimes with spacelike past infinity such as de Sitter spacetime. In
particular, we remind the reader of a general formula which gives the field for
given initial data on a Cauchy surface and a given source (a charge or
stress-energy tensor distribution) in its future. We then apply this formula to
three examples: (i) electromagnetism in the future of a Cauchy surface in
Minkowski spacetime, (ii) electromagnetism in de Sitter spacetime, and (iii)
linearized gravity in de Sitter spacetime. In each example the field is
reproduced correctly as predicted by the general argument. In the third example
we construct a linearized gravitational field from two equal point masses
located at the "North and South Poles" which is non-singular on the
cosmological horizon and satisfies a covariant gauge condition and show that
this field is reproduced by the retarded Green's function with corresponding
gauge parameters.
