Spectral distortion signatures of step-like inflationary potential

Abstract

In this work, we analyze a power-law inflationary potential enhanced with a step that can introduce features in the primordial power spectrum. We focus on the computation of the Spectral Distortions (SD) induced by these features obtained from the inflationary dynamics. In this scenario, we explore the potential of upcoming experimental missions like PIXIE to detect the SD of the model within a power of n = 2/3, a power that agrees with recent tensor-to-scalar ratio constraints. The model offers insights into models with cosmological phases and different scalar field dynamics. Introducing a step in the inflaton potential leads to distinct features in the primordial power spectrum, such as oscillations and localized enhancements/suppressions at specific scales. We analyze the impact of three primary parameters — β, δ, and ϕ step — on the amplitude and characteristics of the SD. The ϕ step places the onset of the oscillations in the primordial power spectrum. The β parameter significantly influences the magnitude of the μ-SD, with its increase leading to larger SD and vice versa. Similarly, the δ parameter affects the smoothness of the step in the potential, with larger values resulting in smaller SD. Our findings indicate a distinct parameter space defined by 0.02 < δ/Mpl ≲ 0.026, 0.10 ≲ β < 0.23, and 7.53 ≲ ϕ step/ Mpl ≲ 7.55, which produces SD potentially detectable by PIXIE. This region also corresponds to the maximum observed values of μ and y SD, which in special cases are an order of magnitude larger than the expected for ΛCDM. However, we also identify parameter ranges where μ and y SD may not be detectable due to the limitations of current observational technology. This comprehensive analysis of SD provides constraints of step-like inflationary models and their implications on its dynamics.