Chapter 14: Intermediate Frequencies

While the low-frequency gravitons primarily affect the temperature and the polarization anisotropies of the CMB, a number of different phenomena occur in the intermediate range that extends for about 12 orders of magnitude from the pHz range to a fraction of the Hz. In this region, the spectra are bounded by the millisecond pulsar’s pulses and are also constrained by the success big-bang nucleosynthesis (BBN). While the limits discussed here are crucial for various unconventional scenarios, they are however immaterial for the concordance paradigm where the expected signal remains always much smaller than the potential constraints. The variety of the phenomena and their phenomenological relevance explains why the first section is now devoted to a more thorough discussion of the general logic of the chapter.