Symmetry-Protected $\alpha$-Attractor Hybrid Inflation in Supergravity and Constraints from ACT DR6 and DESI DR2

Abstract

We present a symmetry-protected supergravity realization of hybrid $\alpha$-attractor inflation with a constant sequestered uplift. The model achieves an exact analytic embedding of the attractor geometry while maintaining vacuum stability and radiative control. The uplift, generated by a hidden St\"uckelberg $U(1)_D$ sector, preserves the inflaton dynamics and provides an independent handle on the post-inflationary vacuum energy. The framework yields precise next-to-leading-order predictions for the scalar spectral tilt and tensor amplitude, fully consistent with current ACT DR6, DESI DR2, and Planck data. Radiative and geometric corrections remain exponentially suppressed, ensuring the robustness of the inflationary trajectory. This construction offers a minimal, UV-complete, and testable benchmark for embedding $\alpha$-attractor inflation in supergravity, with tensor modes potentially observable by LiteBIRD and CMB-S4.