Relaxation-Driven Cyclic Cosmology (RDCC) v28.0 - Minimal Extension of ΛCDM / Bounce EFT Framework

Relaxation-Driven Cyclic Cosmology (RDCC) v28.0 is a major refinement of the RDCC framework, a minimal and nonsingular extension of ΛCDM based on the postulate that the global quantum state of the Universe is a CPT eigenstate. This structural principle enforces a two-sector Hilbert-space factorization in which the visible and mirror sectors propagate on the same spacetime geometry and interact only through gravity. A single infrared relaxation parameter, α ~ 10⁻², generated by a Planck-suppressed operator, governs all observable deviations from ΛCDM. Version 28.0 introduces several important improvements and clarifications: • A fully polished and reorganized presentation of the scalar-field dynamics, including the radiatively generated Higgs-sector potential and the cuscuton-like kinetic correction responsible for the smooth, ghost-free bounce. • A unified and streamlined treatment of cosmological perturbations, including the entropic mechanism that converts isocurvature modes into adiabatic curvature perturbations and yields the prediction nₛ − 1 = −2α. • A refined analysis of the mirror sector as a natural dark-matter candidate, including the dynamically generated temperature ratio x = T'/T ≃ 0.5 and the relaxation-driven attractor for Ω_DM / Ω_b. • Expanded forecasts for Euclid, DESI, SKA, and LISA, emphasizing the percent-level suppression of fσ₈(z), the correlated prediction ΔN_eff ≃ 0.1–0.3, and the blue-tilted stochastic gravitational-wave background peaking at 10⁻³–10⁻² Hz. • A significantly improved Discussion and Conclusion section, clarifying RDCC’s relationship to inflationary and CPT-symmetric cosmology, and highlighting the model’s one-parameter falsifiability structure. • Numerous stylistic, structural, and conceptual refinements across all sections to improve clarity, consistency, and scientific accessibility. RDCC v28.0 provides a coherent, radiatively natural, and observationally testable alternative to inflationary cosmology. Its predictions span CMB physics, large-scale structure, 21-cm cosmology, and gravitational-wave astronomy, offering a sharply constrained multi-observable signature pattern that upcoming experiments — including CMB-S4, Euclid, DESI, SKA, and LISA - will be able to test. Related documents and the full RDCC ecosystem are available via Zenodo:https://zenodo.org/records/18204087 Michael [email protected]