Reinterpreting the Lamb Shift as a Finite Interface Effect A Structural Perspective on Short–Range Atomic Physics

This paper revisits the physical interpretation of the Lamb shift, one of the most precisely calculated observables in atomic physics. While its quantitative description within bound-state quantum electrodynamics is firmly established, the shift is commonly understood only as a formal sum of short-distance corrections. The present work proposes a conservative reinterpretation in which the Lamb shift is viewed as the response of a finite interaction interface between bound particles. No modifications to existing QED calculations are introduced. Instead, the analysis emphasizes how the known short-range sensitivity of the Lamb shift naturally admits a reduced-mass–dependent structural interpretation. This perspective provides a coherent physical picture linking radiative, recoil, and finite-size effects, and connects directly to modern high-precision measurements in hydrogenic systems.