Relaxation-Driven Cyclic Cosmology (RDCC) v27.0 - Minimal Extension of ΛCDM / Bounce EFT Framework

Relaxation‑Driven Cyclic Cosmology (RDCC) v27.0 is a major refinement of the framework, consolidating its conceptual structure, EFT consistency, and observational testability. This version introduces a fully revised abstract, a high‑impact conclusion, and a new dedicated section on Euclid forecasts, including an illustrative growth‑rate comparison between RDCC and ΛCDM. The document has been reorganized for clarity, minimality, and scientific coherence, with improved explanations of the CPT‑symmetric two‑sector structure, the role of the relaxation parameter α, and the entropic mechanism generating the primordial tilt. What’s new in v27.0: Rewritten Abstract: Clearer logical structure, improved explanation of the perturbation mechanism, EFT validity, and observational predictions. High‑Impact Conclusion: Stronger synthesis of the model’s implications, testability, and conceptual minimality. New Euclid Forecast Section: Introduces percent‑level predictions for fσ8(z), discusses Euclid DR1/DR2 relevance, and includes a schematic RDCC vs. ΛCDM growth‑rate figure. Improved EFT Discussion: Clearer presentation of the cuscuton‑like operator, positivity bounds, and bounce regularity. Refined Perturbation Narrative: More precise description of isocurvature–adiabatic conversion and the entropic origin of the spectral tilt. Enhanced Structure and Readability: Streamlined sections, consistent notation, and improved conceptual flow across the entire document. RDCC v27.0 represents the most polished and coherent formulation of the framework to date, preparing the ground for future technical developments in v28.x, including perturbation stability analysis, α‑derivation, and numerical fits to Euclid, DESI, and CMB‑S4 data. Related documents and the full RDCC ecosystem are available via Zenodo:https://zenodo.org/records/18204087 Michael [email protected]