Gravity as Pressure Gradient: A Hydrodynamic Vacuum Model of Gravitational Radiation (Companion Preprint)

This preprint is a technical companion to “Gravity as Acoustic Radiation Pressure.” It reformulates the same underlying premise in a pressure-gradient language: if the vacuum is treated as an effective, self-sustained medium, then static gravitation corresponds to a spatial pressure gradient and gravitational radiation corresponds to propagating compressional disturbances of that medium. The purpose is not to claim experimental confirmation, but to provide a transparent mapping between a hydrodynamic/acoustic description and standard gravitational observables under clearly stated assumptions. Using Lighthill’s acoustic analogy and the standard quadrupole framework, the paper derives an energy-loss expression with the same leading-order dependence on mass, separation, and frequency as the Peters–Mathews result for compact binaries. The overall coefficient is matched via an explicit mapping between Newton’s constant and an effective background density scale; this fixes a single correspondence constant rather than constituting an independent prediction. A key potential discriminator from General Relativity is identified: the angular distribution and polarisation content of the radiated field in the medium description. Open problems are stated explicitly, including the mechanism by which a pure spin-2 mode would emerge (or be selected) from collective excitations of the medium, and the phase-locking mechanism required for long-lived sources. The paper concludes with testable implications and clearly distinguishes derivations within the model from speculative extensions. Companion preprint (primary framework): 'Gravity as Acoustic Radiation Pressure' 10.510.5281/zenodo.18646470