Physical unit systems establish the fundamental measurement conventions—such as CGS, Gaussian, Heaviside-Lorentz, and natural units—used to express quantities consistently in quantum field theory, where dimensional analysis verifies equation consistency and derives relationships between physical quantities. Natural units set fundamental constants (speed of light, reduced Planck's constant, gravitational constant) to unity, simplifying the equations of quantum field theory, clarifying the physical interpretation of quantities like mass and energy, and supporting renormalization procedures that require careful, consistent unit tracking. This subject sits within theoretical physics as a foundational convention layer underlying the formalism of quantum field theory and its relation to special relativity.
Physical unit systems establish the fundamental measurement conventions—such as CGS, Gaussian, Heaviside-Lorentz, and natural units—used to express quantities consistently in quantum field theory, wh…