Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Generalized Parton Distributions and Their Singularities   A new approach to building models of generalized parton distributions (GPDs)
is discussed that is based on the factorized DD (double distribution) Ansatz
within the single-DD formalism. The latter was not used before, because
reconstructing GPDs from the forward limit one should start in this case with a
very singular function f({\beta})/{\beta} rather than with the usual parton
density f({\beta}). This results in a non-integrable singularity at {\beta}=0
exaggerated by the fact that f({\beta})'s, on their own, have a singular
{\beta}^{-a} Regge behavior for small {\beta}. It is shown that the singularity
is regulated within the GPD model of Szczepaniak et al., in which the Regge
behavior is implanted through a subtracted dispersion relation for the
hadron-parton scattering amplitude. It is demonstrated that using proper
softening of the quark-hadron vertices in the regions of large parton
virtualities results in model GPDs H(x,{\xi}) that are finite and continuous at
the "border point" x={\xi}. Using a simple input forward distribution, we
illustrate implementation of the new approach for explicit construction of
model GPDs. As a further development, a more general method of regulating the
{\beta}=0 singularities is proposed that is based on the separation of the
initial single DD f({\beta}, {\alpha}) into the "plus" part
[f({\beta},{\alpha})]_{+} and the D-term. It is demonstrated that the "DD+D"
separation method allows to (re)derive GPD sum rules that relate the difference
between the forward distribution f(x)=H(x,0) and the border function H(x,x)
with the D-term function D({\alpha}).

21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol