Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Systematics in nucleon matrix element calculations   The current status of calculations of simple nucleon structure observables is
reviewed, with a focus on the axial charge. A major challenge is the
combination of an exponentially decaying signal-to-noise ratio and the need for
large source-sink separations to eliminate excited-state contributions; efforts
to understand and deal with this problem are the focus of the largest section
of this review. Finite-volume effects and chiral extrapolation are also briefly
discussed.

15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph