On the Emergence of a Universal Structural Invariant in a Pre-Metric Informational Field Framework

This paper presents a mechanism by which a universal propagation bound, identified with the speed of light, emerges naturally within the Λ-Convergence Unified Field Theory (LUFT). Rather than assuming a spacetime metric or postulating a fundamental constant, LUFT is formulated as a pre-metric informational framework defined by three primitive structures: a propagation field, a scalar potential, and a global coherence principle. By analyzing the constitutive response of the vacuum and the associated Fresnel polynomial, the paper demonstrates that: • Any stable vacuum configuration admits a finite upper bound on information propagation.• This bound is invariant and observer-independent.• Massless excitations propagate at the limiting bound.• Lorentz symmetry emerges as a structural consequence of the informational substrate, not as a postulate. The result is not a numerical derivation of the value of c, but a mechanism-level explanation for why a universal invariant propagation bound arises at all—complementing conventional formulations in which c is introduced as a primitive constant. The paper further identifies a falsifiable observational signature: a wavelength-dependent phase shift in multi-wavelength interferometry governed by a phenomenological coherence scale. This work constitutes part of the broader LUFT research program, which investigates how geometric, gravitational, and dynamical structures may emerge from deeper informational principles. *This version refines the presentation and scope of the derivation, clarifies assumptions, and prepares the framework for subsequent papers. The core results are unchanged.