Swampland bound on quintessential inflation in IDM

TL;DR

This paper explores a model of quintessential inflation within the Inert Doublet Model, analyzing its dynamics, observational predictions, and tensions with swampland conjectures, highlighting the need for extremely weak coupling to match current cosmological data.

Contribution

It introduces a two-field quintessential inflation model in IDM, derives its effective potential, and compares its predictions with observational and swampland constraints, revealing a significant tension.

Findings

Weak quintessence-inflaton coupling is required by CMB data.

Swampland dS conjecture favors a steeper potential with larger eta.

Tension exists between quantum gravity constraints and cosmological viability.

Abstract

We study a quintessential inflation scenario based on the Inert Doublet Model (IDM) coupled to a quintessence field via an exponential potential $V_0e^{-\beta\phi/M_p}$. Using a conformal transformation from the Jordan frame to the Einstein frame, we derive an effective Starobinsky-type potential modulated by an exponential factor that naturally unifies the inflationary epoch with the late-time accelerated expansion of the Universe. We analyze the resulting two-field dynamics, compute the slow-roll parameters, the primordial perturbation spectrum, as well as the inflationary observables $n_s$ and $r$, and then confront the predictions with the latest $Planck$ and $BICEP/Keck$ data. We find amongst others that the quintessence inflaton coupling must remain extremely weak, in the order of $\beta \lesssim 4\times10^{-3}$, to satisfy current $CMB$ data, whereas swampland dS conjecture favors a step potential with $\beta\sim\mathcal{O}(1)$, signaling a significant tension between quantum gravity consistency and cosmological viability. We conclude by discussing possible extensions and stabilization mechanisms that could help reconcile the inflationary predictions with swampland constraints.