Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An a posteriori error estimate of the outer normal derivative using dual
  weights   We derive a residual based a-posteriori error estimate for the outer normal
flux of approximations to {the diffusion problem with variable coefficient}. By
analyzing the solution of the adjoint problem, we show that error indicators in
the bulk may be defined to be of higher order than those close to the boundary,
which lead to more economic meshes. The theory is illustrated with some
numerical examples.

17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th