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Abstract

A standalone short note transcribing the separate-universe failure criterion, spun out of A3M's Appendix A (no new math introduced beyond the source theory-audit note). It derives the exact threading identity between the comoving curvature perturbation and the separate universe's zero-shift variable, and states when the separate-universe method reproduces the squeezed-limit bispectrum and when it does not.

Result summary

• derivedExact threading identity between Maldacena's comoving ζ and the separate universe's zero-shift variable δN_c
• openCriterion: δN (isotropic, N(φ,π)) reproduces the squeezed bispectrum of ζ iff the ζ-growth-weighted mean ⟨ε/c_s²⟩_ζ vanishes
• openDust contraction: O(1) failure, monopole gap 25/8
• openUltra-slow-roll inflation: agreement to O(ε), reproduces Namjoo-Firouzjahi-Sasaki 2013

Readiness

0B / 0M / 0m / 0C open

Readiness is publication readiness only — science, evidence, review convergence, packaging, and Houston’s final sign-off. Venue and submission are tracked separately below, and never subtract from this number (directive P).

Publishing

Not part of readiness.

Lineage

Short note · Separate-universe failure criterion. This work does not claim beyond its stated target and scope above.