|Φ|^8 Extension: Cosmological Evasion, Spectral Stability and Quantum Robustness - Consolidated Sealed Record

Technical Note R11.5 of the Quantum Phase Constitutive Theory (QPCT) investigates whether the cosmological no-go theorem established in earlier stages of the programme — which forbade accelerated expansion within the minimal single-field framework — can be evaded by extending the scalar potential with a higher-order operator. The note demonstrates, through a complete and audited derivation chain, that such evasion is not only possible but structurally robust: there exists an open, positive-measure region of parameter space in which the background condensate simultaneously satisfies the conditions for accelerated expansion, radial stability, real condensate frequency, and positive energy density. The full spectrum of quadratic fluctuations around this background is shown to be free of ghosts, tachyons, and gradient instabilities, and the Hamiltonian is proven to be positive definite. An effective field theory for the Goldstone phase mode is derived at tree level and shown to be local, unitary, and ghost-free with a well-defined sound speed strictly between zero and one. Finally, the classical results are shown to survive at the one-loop quantum level under an explicit perturbativity condition. The physical content of the programme is thereby closed; the sole item delegated to a subsequent block is the determination of exact numerical coefficients in the quantum corrections, which does not affect any of the structural conclusions.