Type: Article
Publication Date: 2019-12-11
Citations: 42
DOI: https://doi.org/10.1103/physrevd.100.123516
Weyl (scale)-invariant theories of scalars and gravity can generate all mass scales spontaneously. In this paper, we study a particularly simple version---scale-invariant ${R}^{2}$ gravity---and show that, during an inflationary period, it leads to fluctuations which, for a particular parameter choice, are almost indistinguishable from normal ${R}^{2}$ inflation. Current observations place tight constraints on the primary coupling constant of this theory and predict a tensor to scalar ratio, $0.0033>r>0.0026$, which is testable with the next generation of cosmic microwave background experiments.