Observational constraints on inflationary decoherence with polynomial attractor model

Abstract: The quantum-to-classical transition of inflationary perturbations remains an unresolved fundamental problem, and quantum decoherence is one of the promising solutions. By considering quantum perturbations during inflation as an open quantum system interacting with its environment, quantum decoherence can be described by the Lindblad equation. This formalism modifies the evolution of primordial quantum perturbations and consequently alters the power spectrum of curvature perturbations, leading to observable consequences. In this paper, we examine the decoherence process of a polynomial attractor model featuring an ultra-slow-roll stage, extending previous analyses limited to slow-roll scenarios. We numerically compute the correction to the power spectrum due to quantum decoherence, and the results show significant modification only on large scales, with a peak generated by the decoherence correction at the minimum of the power spectrum. Using observational constraints on the scalar spectral index and the tensor-to-scalar ratio, and requiring complete decoherence for relevant scales by the end of inflation, we obtain the constraint on the interaction parameter as $10^{-17}\text{Mpc}^{-1}<k_\gamma<0.061\text{Mpc}^{-1}$.