4.4.3. Tensor and vector modes

Large-scale tensor modes are a generic prediction of inflation, but unfortunately the amplitude depends on the inflation model and there is no automatic implication that the tensor modes will have sufficient amplitude to be detectable by forseeable technology (indeed if anything theoretical prejudice suggests the opposite [22]). If tensor modes are discovered, for example by the Planck satellite, that will be exceedingly strong support for inflation. However tensor modes do not formally constitute a test of inflation, since their absence does not exclude the paradigm.

By contrast, the simplest inflationary models do not produce vector perturbations. If those are seen, then at the very least it will represent a considerable challenge to model-builders to find a way of accounting for them from within the inflationary paradigm.