Pressure-Driven Gravity as a Superfluid Vacuum Theory - Ylia Callan - 3 August 2025

This thesis explores the hypothesis that spacetime is not empty but behaves as a relativistic superfluid, with gravity emerging from pressure gradients rather than spacetime curvature. Building on microphysical models involving axion-like particles and spin-2 Bose-Einstein condensates, the framework predicts phenomena not accounted for by General Relativity: frequency-dependent gravitational wave dispersion (detectable by LISA), spectral distortions in the CMB (PIXIE/PRISM), and energy dependent neutrino delays (IceCube). The theory addresses longstanding problems in cosmology - such as structure formation, inflation, dark energy, and the Hubble tension - while remaining consistent with classical tests of gravity, including Mercury’s perihelion shift. This falsifiable, experimentally grounded alternative challenges the geometric paradigm of gravitation and proposes a new field - theoretic ontology of spacetime.