Fermi Bubbles as the Upper Bound of Space-Phase Stiffness: Volumetric Conditioning Across Galactic Scale

Earlier SP3 work introduced a stiffness-across-scale ladder, anchored by coronal massejection expansion, planetary orbital persistence, Event Horizon Telescope ring coherence,and more recently the RBH‑1 recoil wake. In this paper, that ladder is extended to its largestobservational scale so far using the Fermi bubbles—bipolar, kiloparsec-scale lobesemerging from the Galactic center and persisting for millions of years. Using the sameoperational definition of stiffness as resistance to lateral relaxation and coherence loss, theFermi bubbles are shown to represent volumetric, long-duration conditioning of the spacephase medium. Their sharp boundaries, bilateral symmetry, and longevity establish thestrongest empirical constraint yet on space-phase stiffness, without redefining stiffness ormodifying earlier analyses.