Structural Incompatibility Between the UAT/UCP Framework and Standard Cosmological Boltzmann Solvers: Technical Requirements and Current Limitations

This Zenodo repository contains a technical note on the structural incompatibility between the UAT/UCP framework and standard cosmological Boltzmann solvers such as CLASS and CAMB. The Unified Applicable Time (UAT) and Unified Causal Principle (UCP) framework is an independent descriptive metric of reality. It is not an extension of the standard Lambda-CDM model and does not assume the standard Friedmann-Lemaître-Robertson-Walker metric or standard conformal time as fundamental. This note documents why UAT/UCP cannot be implemented in existing solvers by simply adjusting parameters. A faithful implementation would require rewriting the core structural modules of a Boltzmann code: Background evolution Perturbation equations Primordial initial conditions Line-of-sight transfer functions The standard shortcuts, such as inserting a modified H(z) into a standard solver, produce hybrid results that do not represent the full UAT/UCP model. Currently, no functional UAT/UCP Boltzmann solver exists. As a consequence, the CMB and large-scale structure predictions of the framework remain limited to analytical and semi-analytical approximations. This note does not propose modifications to the source code of any existing solver. It records the technical boundaries that must be respected by future numerical work and outlines the requirements for a dedicated UAT/UCP solver. The limitation is technical, not observational. It does not refute UAT/UCP, but it prevents full CMB and structure-formation predictions until the necessary numerical infrastructure is built.