Quantum Vacuum as a Viscous Relativistic Fluid

We propose a model of the quantum vacuum as a relativistic viscous fluid with a fundamental cutoff at Planck pressure. The model incorporates a scale-dependent viscosity that modifies the propagation of fields in vacuum and introduces dissipative dynamics. From an effective field theory (EFT) perspective, we construct an action including fluid-like degrees of freedom, quantum corrections, and an emergent gravitational term analogous to Sakharov's induced gravity [1,2]. We analyze the resulting dynamics, derive observable consequences such as photon attenuation, energy-dependent propagation, and corrections to the Unruh and Casimir effects are derived [3,4]. The model bridges quantum field theory, hydrodynamics, and emergent gravity, offering a new perspective on the physical nature of the vacuum. We also explore hypothesis proposed by Scarmato [10] that the speed of light in vacuum emerges as a limiting velocity due to a viscous interaction between photons and the quantum vacuum. By modeling the vacuum as a fluid with energy density, the author proposes that light is subject to a Stokes-like drag force, causing an initial deceleration to the universal constant . This model reintroduces the notion of an ether within a modern quantum framework and raises new perspectives on gravitation, refraction, and cosmology.