Confronting Mukhanov Parametrization of Inflationary Equation-of-State with ACT-DR6

TL;DR

This paper tests Mukhanov's inflationary equation-of-state parametrization against recent ACT-DR6 data, constraining model parameters and exploring the impact of future CMB observations on the viability of the model.

Contribution

It introduces a semi-analytical approach to compare Mukhanov parametrization with latest data and constrains its parameters using current and forecasted CMB observations.

Findings

Excellent fit of the model to current data.

Stringent constraints on parameters $eta$ and $eta$ from data and gravity wave limits.

Future CMB missions can significantly narrow the parameter space.

Abstract

We provide a simple yet effective semi-analytical approach to confront Mukhanov Parametrization of inflationary equation-of-state, $1+\omega =\frac{\beta}{({N}+1)^\alpha}$, with the latest ACT-DR6 data employing Hamilton-Jacobi formulation. We find that equation-of-state formalism comes up with excellent fit to the latest data. In the process we are also able to put stringent constraint on the two model parameters. In order to get the bounds of $\alpha$ and $\beta$ we have also made use of the recent finding $r<0.032$. We have further utilized results from the joint analysis of ACT-DR6, Planck-2018 and DESI-Y1 data to find the observationally viable region for $\alpha$ and $\beta$. We have also employed the predictions on primordial gravity waves from forthcoming CMB missions in the likes of CMB-S4 and LiteBIRD along with results from the combination of ACT-DR6, Planck-2018 and DESI-Y1 data to further restrict the model parameters. We find that detection of gravity waves would help us narrow the viable parameter space for Mukhanov parametrization. But in the absence of detection of primordial gravity waves signal by those CMB missions parameter space is reduced significantly for $\beta$, while the range for $\alpha$ is slightly increased. In addition we observe that, $\alpha$ is primarily dependent on the observationally viable range for scalar spectral index while other model parameter $\beta$ is resting heavily on the restriction upon the amplitude of primordial gravity waves. We find that equation-of-state formalism has a wide range of parameter values consistent with recent observational data set along with futuristic CMB missions in the likes of CMB-S4 and LiteBIRD.