The Standard Model's QCD Lagrangian contains a parameter θ-bar that allows CP violation in strong interactions. Experimental neutron-EDM limits constrain |θ-bar| < 10⁻¹⁰, an extreme fine-tuning since no Standard-Model symmetry requires θ-bar = 0 (Peccei & Quinn 1977; Lu 2024). The Peccei-Quinn axion solution remains experimentally unverified and faces severe quality + cosmology tensions.
The standard model treats θ-bar as an unexplained input that must be fine-tuned to less than 10⁻¹⁰. Recovering this naturally within ΛCDM requires either the Peccei-Quinn axion mechanism (with associated cosmological problems) or other beyond-SM physics. The fine-tuning has no source in the framework itself.
SCT replaces the hot-dense-center with a superluminal collision and the thermalized debris field, with eternal time and infinite Big Bang events. From this single change, the Strong CP problem dissolves through eternal-cycle dynamics. The Standard Model continues to admit a CP-violating θ-bar parameter, but in SCT θ-bar drifts across many prior cycles via QCD dynamics plus cascade-thermalization erasure (P1, P27, P28).
Across the eternal infinite manifold (P1) plus infinite array of Big Bang events (P27, P28), θ-bar evolves through a combination of QCD dynamics inside each cycle (where some equilibration toward smaller |θ-bar| occurs) plus cascade-thermalization at every cosmic-cycle event (which can reset or modify the inherited θ-bar). The cumulative effect across the infinite cycle history is dynamical-plus-anthropic selection toward small |θ-bar| values: cycles with large |θ-bar| produce stable atomic structures with too-strong neutron EDMs to support complex chemistry, so observers exist preferentially in cycles where |θ-bar| is small.
The resolution requires no axion field. The mechanism uses Standard Model QCD physics (which is unmodified) plus the cosmological framework of eternal cycles (P1, P27, P28) plus the cascade-thermalization erasure mechanism (P22, P25). Pre-existing matter inherited from prior cycles (P25) with already-small |θ-bar| is what gets thermalized into our cycle's matter content. The same M11 framework that resolves the metallicity floor (recid 125), the FRB diversity (recid 153), and the broader pre-existing-matter context phenomenology accounts for the Strong CP problem without invoking the axion or other beyond-SM mechanisms.
Detection of an axion with the predicted Peccei-Quinn properties at greater than 5σ would be consistent with axion-based CP solution but would not directly refute the M11 explanation (axion + eternal cycles could co-exist). Direct measurement of |θ-bar| near 1 in any cosmological context would refute the eternal-cycle dynamical-selection mechanism.