Is there a spatial gradient in values of the fine-structure constant? A reanalysis of the results (Research Note).

We statistically analyse a recent sample of data points measuring the fine-structure constant a (relative to the terrestrial value) in quasar absorption systems, where a spatial gradient in a was recently reported. We find agreement with previous authors that the dipole model is a robust, well-justified fit to the data. Using a simple analysis we find that the monopole term (the constant offset in Δα/α) may be caused by non-terrestrial magnesium isotope abundances in the absorbers. Finally we test the domain-wall model against the data. [ABSTRACT FROM AUTHOR]