Varying electric charge in multiscale spacetimes

TL;DR

This paper develops a covariant framework for electrodynamics in multiscale spacetimes, predicting a natural variation of the electric charge and fine-structure constant, and compares it with other varying-coupling models and cosmological data.

Contribution

It introduces a novel multiscale spacetime model with a geometric origin for varying electric charge, distinct from previous varying-e or varying-c models.

Findings

Effective spacetime-dependent electric charge emerges naturally.

Constraints on model scales from cosmological observations.

Comparison with other varying-coupling theories.

Abstract

We derive the covariant equations of motion for Maxwell field theory and electrodynamics in multiscale spacetimes with weighted Laplacian. An effective spacetime-dependent electric charge of geometric origin naturally emerges from the theory, thus giving rise to a varying fine-structure constant. The theory is compared with other varying-coupling models, such as those with a varying electric charge or varying speed of light. The theory is also confronted with cosmological observations, which can place constraints on the characteristic scales in the multifractional measure. We note that the model considered here is fundamentally different from those previously proposed in the literature, either of the varying-e or varying-c persuasion.