Varying electric charge in multiscale spacetimes
  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.
