A Calibrated Two-Phase Eective-Field-Theory Benchmark for Matter Production from a Tachyonic Scalar Vacuum: Construction, Diagnostics, and Open Problems

We present a speculative, explicitly calibrated eective-eld-theory (EFT) benchmark inwhich a matter-free scalar eld conguration (PHASE 1) transfers a nite energy reservoirinto baryon-charged and dark sectors (PHASE 2). Absolute vacuum is used operationally:PHASE 1 contains quantum elds and stored energy but no baryonic matter, dark matter,or classical radiation; it is not metaphysical nothingness. The parent is a real scalar with asymmetric double-well potential V = λ(Φ2 − v2)2/4, whose origin is a tachyonic hilltop, nota metastable false vacuum. Conditional on a late quasiparticle regime, perturbative parentdecay populates two real heavy resonances X1,2 and a light scalar s. A non-Hermitian 2×2eective Hamiltonian for the resonances, with prescribed dispersive input, gives an integratedcharge asymmetry AB = 0.254577; the probabilities sum to unity to machine precision, whichis a structural property of the formalism (Appendix B). The energy partition ρB = 197.59216,ρbookD = 998.33834 (ratio 5.05252) is imposed through a branching-ratio calibration of theportal gs and is not a prediction. New quantitative diagnostics are reported: domain-wallenergy is of the same order as the reservoir (σ/Ldom ≃ 0.73ΔV ); a Floquet analysis showsthat induced production on a coherent background exceeds the vacuum width by factors from∼ 6 × 102 to ∼ 3 × 104 for amplitudes A ≳ 0.05 μ0, so the vacuum-width treatment cannotdescribe the early stage; a naive complete-thermalization estimate gives T ∼ 0.9MX and anet charge-to-entropy ratio about 2 × 109 times the observed baryon-to-entropy ratio; anda scan of the dispersive input shows |AB| ≤ 0.2604 for this texture, with the benchmark at97.8% of that maximum. A separate U(4)-motivated soft-matching construction is presentedas an auxiliary parametrization whose conditional quadratic sensitivity is derived, while itsradiative protection and the associated residual-vacuum fraction (1+√3)/4 remain unproven.The paper therefore provides a reproducible reduced calculation, a catalogue of what has andhas not been demonstrated, and an explicit validation roadmap, rather than a cosmologicaltheory.