  I report theoretical predictions of two models of donor-donor indirect
interaction mediated by photons in zero- and two-dimensional cavities. These
results are compared to previously studied cases of indirect interactions
mediated by excitons and/or polaritons in bulk semiconductor and
two-dimensional cavities. I find that photons mediate an Ising-like interaction
between donors in the same manner polaritons do, in contrast to the
Heisenberg-like interaction mediated by exciton. For the particular case of a
two-dimensional cavity, the model shows that the dependence on distance of the
donor-donor coupling constant is the same for photons and polaritons when the
donor-donor distance is large. Then, it becomes clear that photons are
responsible for the long range behavior of the polariton indirect interaction.
