Imaginary Kerr Horizons in Ordinary Rotating Matter: A New Geometric Property and Its Connection to the Universal 1–5 Hz Signal

The Kerr metric, applied without modification to any non-collapsed rotating collective excitation in ordinary matter, yields an imaginary outer horizon r+ ≈ I J/(Mc) whenever the spin parameter a = J/(Mc) greatly exceeds the gravitational radius Rg = GM/c2. This mathematical structure corresponds to a negative contribution to the effective stress-energy tensor of common matter. Since every non-collapsed rotating body satisfies a ≫ Rg, these are not exotic properties of special objects. They are new geometric characteristics of ordinary matter. The mass did not change; we have identified two new mathematical expressions of what it does. The ubiquitous 0.5 – 5 Hz hum observed in all precision instruments is proposed as a possible empirical signature of these geometric effects, leading to the discovery of the vacuum granule mass (ref. A9). A key result of this version: for a single vacuum granule of mass M ≈ 10−44 kg, the imaginary Kerr horizon scale |r+| = ℏ /(Mc) ≈ 35m and the Compton wavelength λC = h/(Mc) ≈ 220m. For the full A9 granule mass range, both scales fall between 3.5m and 22km — directly within the geometric scale of LIGO, Virgo, and the Einstein Telescope, making the findings of this paper practically testable. Full A-series are available in A9 description https://zenodo.org/records/18888582