Chapter 5: Effective Actions

In flat space–time the evolution of the tensor modes follows either from the equations or motion perturbed to first-order or from the second-order fluctuations action. In curved backgrounds the same strategy discussed in the Minkowski case (see Chapter 2) leads to the effective action of the relic gravitons and also suggests a sound definition of their energy–momentum pseudo-tensor that is explicitly discussed in Chapter 7. The present and the following three chapters also address a series of related topics that are relevant for the forthcoming phenomenological applications…