Attempts at a determination of the fine-structure constant from first principles: A brief historical overview

TL;DR

This paper reviews historical and theoretical efforts to derive the fine-structure constant from first principles, discussing approaches based on QED, symmetry groups, and string theory, highlighting their strengths and weaknesses.

Contribution

It provides a comprehensive overview of various theoretical approaches to calculating the fine-structure constant from first principles, including classical, quantum, and string-inspired methods.

Findings

Analysis of the QED beta function approach

Discussion of algebraic identities relating alpha_QED to symmetry groups

Evaluation of string theory inspired models

Abstract

It has been a notably elusive task to find a remotely sensical ansatz for a calculation of Sommerfeld's electrodynamic fine-structure constant alpha_QED ~ 1/137.036 based on first principles. However, this has not prevented a number of researchers to invest considerable effort into the problem, despite the formidable challenges, and a number of attempts have been recorded in the literature. Here, we review a possible approach based on the quantum electrodynamic (QED) beta function, and on algebraic identities relating alpha_QED to invariant properties of "internal" symmetry groups, as well as attempts to relate the strength of the electromagnetic interaction to the natural cut-off scale for other gauge theories. Conjectures based on both classical as well as quantum-field theoretical considerations are discussed. We point out apparent strengths and weaknesses of the most prominent attempts that were recorded in the literature. This includes possible connections to scaling properties of the Einstein-Maxwell Lagrangian which describes gravitational and electromagnetic interactions on curved space-times. Alternative approaches inspired by string theory are also discussed. A conceivable variation of the fine-structure constant with time would suggest a connection of alpha_QED to global structures of the Universe, which in turn are largely determined by gravitational interactions.