A Leading-Order Rational Estimate for Equilateral Non-Gaussianity in the Triptyque Conceptuel

This note is a companion to the Triptyque Conceptuel Version 18 (Zenodo, DOI: 10.5281/zenodo.19423018), which establishes the conformally coupled master equation (□_g + R/6)ψ + ∂V/∂ψ* = 0 as the UV-consistent kinetic operator of a complex scalar field on curved spacetime. The Triptyque Conceptuel describes inflation through a complex scalar field in the Madelung decomposition. The phase degree of freedom δS is a Goldstone boson propagating with sound speed c_S = 1/√2, fixed by the algebraic structure of the model. Using the standard effective field theory of inflation for a Goldstone mode with c_S ≠ 1, we derive a leading-order estimate for the equilateral non-Gaussianity parameter: f_NL^equil,LO = −35/216 ≈ −0.162. This value is a rational number in Q, providing a sharp distinguishing prediction from Starobinsky inflation (which predicts f_NL ≈ 0) despite identical scalar spectral index and tensor-to-scalar ratio. The local non-Gaussianity satisfies f_NL^local ≈ 0, consistent with the single-field consistency relation. Next-order EFT corrections shift the estimate toward f_NL ≈ −0.100. The prediction is potentially testable by Euclid and SKA (σ ~ 0.1) in the 2030s.