What if the Schwarzschild Sign Change is Physical? From Geometry to Physics in a Fully Complexified (3+1) Spacetime

Abstract. The sign change of coordinates at the Schwarzschild horizon is usually treated as a coordinate artefact. This paper treats it as a physical process and follows the consequences. The resulting spacetime is (3+1)C: three complex spatial coordinates zk = xk + i wk (expanded real parts, compact imaginary parts on S3) and one complex time τ = t + iσ (macroscopic real part, compact Euclidean Hawking circle). From the Kähler structure of this spacetime and a single geometric parameter — the Berger deformation ε = 1.01027, fixed by the electron mass — all of fundamental physics follows without additional postulates. Part II derives, before any particle content is specified: the Heisenberg uncertainty relation (from the Kähler form ω = dx ∧ dw), special relativity (as holomorphic symmetry of τ = t+iσ), the dispersion relation E2 = p2c2 + m2 0c4 (as the Pythagorean theorem of the ̄∂-norm), inertia and E = mc2 (as Cauchy–Riemann mismatch resistance), the equivalence principle mi = mg (as a det/tr identity), Einstein’s field equations (from Lovelock uniqueness), the fine-structure constant (from the Sasaki contact structure), and Bose–Einstein condensation and superconductivity (from compact-state coherence under the holomorphic Lorentz boost).Part III derives the complete particle spectrum: the gauge group SU(3) × SU(2) × U(1), the charge, colour, and chirality structure of the Standard Model, three fermion generations (topological; fourth excluded), matter/antimatter distinction, all fermion and boson masses, the electroweak mixing parameters, the CKM matrix at tree level, and the proton mass. In total, ∼ 34 quantitative observables are reproduced with a maximum deviation of 6 % for geometric quantities and 1.3 % for masses. Three independent determinations of ε (from me, mH , and MP ) agree to 370 ppm. The framework makes falsifiable predictions: a mass-ratio-independent remnant spin a∗(q) ≈ 0.69 for binary black-hole mergers (testable with LIGO O4/O5), r = 0 exactly (testable with CMB-S4), and a neutrino luminosity gap in core-collapse supernovae (retro-consistent with SN 1987A to 3 %). The Kähler structure is not an addition to the Standard Model — it is its geometric origin. The Standard Model is the R3,1-projection of a (3+1)C-geometry.