Primordial production of massive relic gravitational waves from a weak   modification of General Relativity
  The production of a stochastic background of relic gravitational waves is well known in various works in the literature, where, using the so called adiabatically-amplified zero-point fluctuations process it has been shown how the standard inflationary scenario for the early universe can in principle provide a distinctive spectrum of relic gravitational waves. In this paper, it is shown that a weak modification of General Relativity produces a third massive polarization of gravitational waves and the primordial production of this polarization is analysed adapting the adiabatically-amplified zero-point fluctuations process at this case. The presence of the mass could also have important applications in cosmology as the fact that gravitational waves can have mass could give a contribution to the dark matter of the Universe. At the end of the paper an upper bound for these relic gravitational waves, which arises from the WMAP constrains, is also released. 
Christian Corda