Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Estimates of $m_d - m_u$ and $\langle\bar{d}d\rangle -
  \langle\bar{u}u\rangle$ from QCD sum rules for $D$ and $D^{\ast}$ isospin
  mass differences   The recent experimental data on $D^{+}-D^{0}$ and $D^{\ast\, +}-D^{\ast\,0}$
mass differences are used as inputs in the QCD sum rules to obtain new
estimates on the mass difference of light quarks and on the difference of their
condensates: $m_d -m_u =3\pm 1\, MeV$, $\langle\bar{d}d\rangle
-\langle\bar{u}u\rangle = -(2.5\pm 1)\cdot 10^{-3}\langle\bar{u}u\rangle$ (at a
standard normalization point, $\mu = 0.5\, GeV$).

5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn