2025/12/16 by Pineda, Flavio, Pimentel, Luis O.
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2512.14455
We study primordial perturbations in Higgs-R2 inflation in the presence of a non-minimal kinetic mixing between the Higgs and the scalaron. By performing a full numerical integration of the multifield background and linear perturbations, we identify distinct dynamical regimes controlled by the non-minimal coupling ξh. For ξh ∼ O(0.1), the turning rate of the inflationary trajectory induces transient multifield effects that imprint localized features in the scalar power spectrum. In the limit ξh≪ 1, the adiabatic spectrum becomes featureless, but isocurvature modes fail to fully decay, leaving a residual contribution at the end of inflation. We compute CMB angular power spectra TT, TE, EE and show how these regimes yield distinct observational signatures, delineating the parameter space compatible with current bounds. Our results highlight that suppressing spectral features does not guarantee the elimination of isocurvature perturbations, placing non-trivial constraints on Higgs-R2 multifield realizations and motivating future probes sensitive to primordial isocurvature.