Inflation in the scale symmetric Standard Model and Weyl geometry

A bstract This work explores the possibility of inflation in a scale-symmetric extension of the Standard Model Higgs sector, where the Higgs field ϕ 1 is coupled to a singlet scalar, the dilaton ϕ 0 . The two-scalar theory is formulated within Weyl geometry, which modifies the Einstein frame form of the resulting single-field inflationary potential. We extend the analysis to include quantum corrections, incorporating curvature effects in the one-loop effective potential. We find that the resulting spectral index n s and tensor-to-scalar ratio r 0.002 can be consistent with the observational constraints. The predicted value r 0.002 ≲ 10 −3 is sufficient to yield a detectable gravitational wave signal. We find the unitarity cutoff in the large-field background, Λ UV ∼ MP/√ξ₁ M P / ξ 1 , which lies below the energy scales relevant during inflation.