Universal Baseline Law — A Unifying Framework for Physical Noise Floors Across Classical and Quantum Domains

This paper presents the Universal Baseline Law, showing that the noise floors of resistors, capacitors, RF systems, Brownian motion, thermomechanical oscillators, magnetic Johnson noise, and Casimir fluctuations all share the same square‑root structure dictated by equipartition, the fluctuation‑dissipation theorem, and phase‑space geometry. By mapping seven independent physical domains onto a single closed‑form expression, the paper demonstrates that the core prediction of Unified Substrate Theory is already verified: every classical and quantum system near equilibrium exhibits the same baseline fluctuation law. This version contains the full derivation, corrected structure, and complete cross‑domain evidence. σ ∝ √( Escale · Nfreedom / κconstraint ) If you have questions or want to discuss the work, you can contact me directly at [email protected]