When Spacetime Coordinates Collapse: Amplitudes as the Relational Replacement
Kacheong R. Yeung, Lex Yeung
This paper argues that amplitude calculus is not an auxiliary quantum construction but the relational coordinate framework forced into existence when the Lorentzian chart collapses at the null boundary. Within the causal domain accessible to a massive probe, the coordinates (x,t) retain clear geometric meaning: worldlines exist, proper time accumulates, and classical trajectories are well defined. At the null boundary these structures fail simultaneously. The invariant interval vanishes, the Lorentzian chart reaches its degenerate limit, and no geometric observable survives. Beyond this boundary the analytic continuation of (x,t) is not spacetime but the diagrammatic overreach of a coordinate system that has exhausted its operational content. Three structural consequences follow. First, null propagation carries no proper time: the boundary is a zero--interval relation, not a limit of motion. Second, the null boundary is not a worldline and admits no geometric in--between. Third, once (x,t) loses operational meaning, only a relational description is possible. In this regime Feynman's amplitude assignments are not postulates but the unique Lorentz--invariant extension assigning complex weights to admissible relational configurations whose coherent aggregate replaces the classical trajectory. Quantum mechanics is thus the relational mathematics demanded by Lorentzian geometry once its coordinates collapse. The non--spacetime domain is not an extension of spacetime but the region where geometry terminates and amplitude begins. This is version 1.1: This version corrects minor structural issues and removes an obsolete appendix; no scientific conclusions are changed. Authors' note (October 2026). This paper is preserved as an exploratory precursor to our later research, not as a validated derivation of quantum mechanics. Several central geometric claims are incorrect: a null interval does not collapse spacetime coordinates to (0,0) or make the Lorentzian metric degenerate, and spacelike-separated events remain part of ordinary spacetime, not a non-spacetime exterior. The further claim that quantum amplitude calculus and complex amplitudes are uniquely forced by null geometry is not established. In particular, the proposed weight e^(−mℓ/ℏ) is a positive real exponential that does not supply the oscillatory relative phases needed for the claimed interference construction; for massless particles (m = 0), this weight is identically one. The original manuscript is retained unchanged as a historical record of the questions that motivated our subsequent investigations. Our later paper, The Lorentz-Analytic Exterior: A Conditional Mathematical Framework (Version 2, October 2026), revisits the geometric and analytic questions under explicit mathematical assumptions, without relying on the coordinate-collapse argument. https://doi.org/10.5281/zenodo.23400176
•May 8, 2026•0 citations