Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Riemann-Hilbert factorization problem for positive definite
  functions   We give several general theorems concerning positive definite solutions of
Riemann-Hilbert problems on the real line. Furthermore, as an example, we apply
our theory to the characteristic function of a class of L\'{e}vy processes and
we find the distribution of their extrema at a given stopping time.

6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con