Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On inverse spectral problems for Sturm-Liouville differential operators
  on closed sets   We study Sturm-Liouville operators on closed sets of a special structure,
which are sometimes referred as time scales and often appear in modelling
various real processes. Depending on the set structure, such operators unify
both differential and difference operators. We obtain properties of their
spectral characteristics and study inverse problems with respect to them. We
prove that the spectral characteristics uniquely determine the operator.

11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th