Primordial gravitational waves by chaotic potential with a sharp step

Abstract

We calculate the primordial gravitational wave spectrum observed today, Ω0gw(f) produced by a chaotic inflationary model featuring a step in its potential. Considering an inflaton field, slowly rolling down the potential, we analyze the scalar and tensor power spectra for the step potential model and found oscillatory density fluctuations within a specific range of wavenumbers around the feature. Localized small anomalies are observed in the tensor power spectrum also. We estimate the observational parameters, including the scalar spectral index (ns), tensor tilt (nt) and tensor-to-scalar ratio (r), which are found to be consistent with Planck satellite results. Additionally, by employing the relation between Ω0gw(f) and r, we determine the effective equation of state parameter wˆ(f) at the end of inflation. Evolution of wˆ(f) from 0.2 to 0.33, followed by constancy is obtained in the ntˆ(f)−wˆ(f) plot. This evolution of wˆ(f) is attributed to the reheating process, which is crucial for transitioning from the inflationary phase to the subsequent radiation-dominated era.