  As first topic, the GDH sume rule is discussed in the context of a more
general class of sum rules associated with the various contributions to the
total photoabsorption cross section for target and beam polarization. Then I
address the question of whether the GDH sum rule for the neutron can be
determined from the one for the deuteron. It appears that this will not be
possible in a simple manner. The spin response of the deuteron is calculated
including contributions from the photodisintegration channel and from coherent
and incoherent single pion production as well, and the GDH integral is
evaluated up to a photon energy of 550 MeV. The photodisintegration channel
converges fast enough and gives a large negative contribution, essentially from
the $^1S_0$ state near threshold and its absolute size is about the same than
the sum of proton and neutron GDH values. It is only partially cancelled by the
single pion production contribution. But the incoherent channel has not reached
convergence at 550 MeV.
