Zero Crossing of the Cosmological Constant in f(R) Asymptotic Safety with Standard Model Matter

Note: This has been amended with improved combined with Paper III's observation that λ (H₀) = 3 Ω_Λ ≈ 2. 06 is also O (1) at the Hubble scale, the 122-order hierarchy between Λₒbs and MPl⁴ arises as the squared ratio of these two boundary scales. It is not a fine-tuning. Combined with Paper I's feedback attractor as the infrared boundary condition and Paper III's two-boundary framework, the trajectory addresses all three aspects of the cosmological constant problem: the old problem (why Λ ≪ MPl⁴), the coincidence problem (why Ω_Λ ∼ Ωₘ), and the determination problem (what fixes Λ). A consistency check against the Friedmann equation with Λ-independent inputs yields Λ = 1. 09 × 10^−52 m^−2, within 1. 3% of the Planck 2018 value. Paper V's spatial ODE method achieves Aₛ within 0. 5 decades of the Planck target at n = 6; closing this gap at higher truncation order (Paper VII) would enable the direct extraction of Λ from the trajectory endpoint. --This is Paper VI of a six-part series, no more papers are planned. Paper I (Salmond 2026, DOI: 10. 5281/zenodo. 20156389): The Cosmological Constant as a Feedback AttractorPaper II (Salmond 2026, DOI: https: //doi. org/10. 5281/zenodo. 20222173): Testing a Connected-Singularity Mechanism for Gravitational Feedback CosmologyPaper III (Salmond 2026, DOI: 10. 5281/zenodo. 20222351): Two-Boundary Determination of the Cosmological Constant from Asymptotic Safety and Gravitational FeedbackPaper IV (Salmond 2026, DOI: 10. 5281/zenodo. 20284172): The Cosmological Constant as a Zero-Parameter Prediction of Asymptotic Safety with Standard Model MatterPaper V (Salmond 2026, DOI: 10. 5281/zenodo. 20286625): Resolving the Spin-2 Boundary Layer in f (R) Asymptotic Safety Paper VI (Salmond 2026, DOI: 10. 5281/zenodo. 20286761): Zero Crossing of the Cosmological Constant in f (R) Asymptotic Safety with Standard Model Matter