Observational constraints on slow-roll inflation coupled to a   Gauss-Bonnet term
  We study slow-roll inflation with a Gauss-Bonnet term that is coupled to an inflaton field nonminimally. We investigate the inflationary solutions for a specific type of the nonminimal coupling to the Gauss-Bonnet term and inflaton potential both analytically and numerically. We also calculate the observable quantities such as the power spectra of the scalar and tensor modes, the spectral indices, the tensor-to-scalar ratio and the running spectral indices. Finally, we constrain our result with the observational data by Planck and BICEP2 experiment. 
Seoktae Koh, Bum-Hoon Lee, Wonwoo Lee, Gansukh Tumurtushaa
gr-qc hep-th