Asymptotics with a positive cosmological constant: II. Linear fields on
  de Sitter space-time
  Linearized gravitational waves in de Sitter space-time are analyzed in detail
to obtain guidance for constructing the theory of gravitational radiation in
presence of a positive cosmological constant in full, nonlinear general
relativity. Specifically: i) In the exact theory, the intrinsic geometry of
$\scri$ is often assumed to be conformally flat in order to reduce the
asymptotic symmetry group from $\Diff$ to the de Sitter group. Our {results
show explicitly} that this condition is physically unreasonable; ii) We obtain
expressions of energy-momentum and angular momentum fluxes carried by
gravitational waves in terms of fields defined at $\scrip$; iii) We argue that,
although energy of linearized gravitational waves can be arbitrarily negative
in general, gravitational waves emitted by physically reasonable sources carry
positive energy; and, finally iv) We demonstrate that the flux formulas reduce
to the familiar ones in Minkowski space-time in spite of the fact that the
limit $\Lambda \to 0$ is discontinuous (since, in particular, $\scri$ changes
its space-like character to null in the limit).
