November 30, 2025International Journal of Modern Physics D5 citations

Viability of generalized α-inflation from Planck, ACT, and DESI Data

Key Points

Inflationary constraints show substantial effects linked to reheating temperature and scalar spectral index, and also depend on decay channels.
Using recent data from Planck and ACT, the study examines generalized inflationary models and their thermal parameters, revealing intriguing dynamics.
Perturbative decay channels like gravitational, Yukawa, and scalar provide insight into model predictions and allowed parameter ranges under observational scrutiny.
The findings highlight the importance of considering CMB+DESI combinations to resolve discrepancies seen within CMB-only analyses.

Abstract

We study inflationary constraints from reheating on two classes of single-field inflationary models: a generalized Formula: see text-attractor with potential Formula: see text and the Formula: see text-Starobinsky model with potential Formula: see text. Using a semi-analytical relation that connects inflationary dynamics to reheating, we solve for the horizon-crossing field value and calculate the scalar spectral index Formula: see text, the tensor-to-scalar ratio Formula: see text, and the reheating temperature Formula: see text. We consider three perturbative decay channels of the inflaton: gravitational, Yukawa (fermionic), and scalar. The parameter space spanned by Formula: see text for the first model and Formula: see text for the second is explored and compared with recent measurements from Planck and ACT DR6, as well as BAO from DESI DR2. For clarity, we emphasize that ACT DR6 alone is fully compatible with Planck regarding Formula: see text. The upward shift toward Formula: see text appears only when DESI DR2 BAO are combined with CMB datasets (Planck+DESI, ACT+DESI, SPT-3G+DESI), and is likewise seen in the P–ACT–LB2+DESI combination. CMB-only combinations (e.g., Planck+ACT or Planck+ACT+SPT-3G) primarily refine constraints and do not by themselves raise Formula: see text. Our comparisons and model assessments are therefore made with this distinction in mind: CMB-only constraints versus CMB+DESI combinations. Within the Formula: see text model, decreasing Formula: see text shifts predictions toward the Formula: see text values preferred by the CMB+DESI combinations, but may yield too-large Formula: see text; we find Formula: see text provides a viable compromise region. For the Formula: see text-Starobinsky case, increasing Formula: see text raises Formula: see text, but values Formula: see text generally exceed observational bounds on Formula: see text. The three decay channels modify the allowed ranges of Formula: see text and Formula: see text, with the scalar channel giving the strongest restrictions. We conclude that both models remain consistent with current CMB-only data in restricted regions of parameter space, and that residual tension with the higher Formula: see text favored by CMB+DESI persists.

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