Vacuum Buoyancy and Cosmic Expansion

This paper explores a fundamental hypothesis: cosmic vacuum is not empty, but has a measurable density, here taken as (60.3 ± 1.3) × 10⁻³¹ g/cm³ (Planck Collaboration, 2021).By introducing the concept of inertial buoyancy of the vacuum, we develop the Φₖ model, which describes how the density and structure of the vacuum influence the expansion of the Universe. Based on observational data (internal galactic pressures, HI gradients, volumes of cosmic winds) and simulations, we show that: Cosmic filaments act as low-inertia resistance corridors, facilitating matter and energy exchanges. Galaxies interconnected by these filaments exhibit coherent and hierarchical internal pressures. Cosmic expansion can be viewed as inertially regulated by the structure of the vacuum, offering an alternative or complement to standard ΛCDM models. All results are presented as falsifiable data (tables, formulas, measured values) enabling independent verification.This approach proposes a unified view linking vacuum density, inertial buoyancy, and cosmic dynamics, opening new perspectives for both observational and theoretical cosmology.