Universality and Robustness of the Coherent Sector in Modal Triplet Theory

We show that the existence, stability, and physical relevance of the coherent sector in Modal Triplet Theory (MTT) are universal within a broad class of geometric and spectral models. Building on the Fixed Points series, the Fundamental Contractivity Condition (FCC), the RG–FCC stability theorem, and constructive results in quantum gravity, we define a coherent universality class characterized by bounded geometry, a uniform spectral gap, and norm-stable coherent projectors. Within this class, the coherent sector persists under curvature perturbations, renormalization-group coarse-graining, and nonperturbative quantum-gravitational dynamics. Calabi–Yau compactifications, heterotic flux vacua (including Strominger systems), and M-theory backgrounds arise as controlled sublimits of the same universality class, while the vast majority of nominal string vacua are excluded by coherence admissibility. As a result, physical predictions in MTT depend only on the coherent universality class rather than on fine-tuned geometric choices, and the string “landscape” is reduced to a sharply constrained admissible set. The analysis is structural and does not rely on detailed internal metrics or parameter tuning, establishing MTT as a universality-based framework.