Renormalization originated as a mathematical technique in Quantum Electrodynamics (QED) to address the ultraviolet (UV) divergences that arise from infinite momentum integrals in virtual particle loops. To extract meaningful physical predictions, physicists introduced regularization schemes (such as dimensional regularization or momentum cutoffs) to temporarily tame these infinite integrals. The divergent parts are then systematically absorbed into the original, unobservable "bare" parameters of the Lagrangian (such as bare mass and bare charge), yielding finite, measurable "renormalized" quantities that correspond to physical reality.

Rather than just a tool to subtract infinities, Kenneth Wilson and others reconceptualized this process as the Renormalization Group (RG)—a profound physical principle describing how a system's effective laws ...