Implications of purely classical gravity for inflationary tensor modes
  We discuss the implications of purely classical, instead of quantum, theory of gravity for the gravitational wave spectrum generated during inflation. We show that a positive detection of primordial gravitational waves will no longer suffice to determine the scale of inflation in this case -- even a high-scale model of inflation can bypass the observational constraints due to large uncertainties in the initial classical amplitude of the tensor modes. 
Amjad Ashoorioon, P. S. Bhupal Dev, Anupam Mazumdar
hep-th astro-ph.CO gr-qc hep-ph