Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A reanalysis of quasar absorption spectra results suggesting a spatial
  gradient in values of the fine-structure constant   We statistically analyse a recent sample of data points measuring the
fine-structure constant alpha (relative to the terrestrial value) in quasar
absorption systems. Using different statistical techniques, we find general
agreement with previous authors that a dipole model is a well-justified fit to
the data. We determine the significance of the dipole fit relative to that of a
simple monopole fit, discuss the consistency of the interpretation, and test
alternate models for potential variation of alpha against the data. Using a
simple analysis we find that the monopole term (the constant offset in (delta
alpha)/alpha) may be caused by non-terrestrial magnesium isotope abundances in
the absorbers. Finally we test the domain-wall model against the data.

8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin