Observational constraints on DBI constant-roll inflation

Understand

Using the constant-roll approach, DBI inflationary scenario will be studied and it is sought to compare the result with observational data.

• By considering the cosmological perturbations of the model, it is realized that some extra terms appear in the amplitude of scalar perturbations which indicate that there shuold be a modified version of the scalar spectral index and tensor-to-scalar ratio.
• In order to compare the model with observational data, some specific functions of scalar field are assumed for the function $f(\phi)$ function.
• For the power-law and exponential functions, a constant slow-roll parameter $\epsilon$ is obtained which produced difficulties for the graceful exit from inflation.