Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multiple nodal solutions to a Robin problem with sign-changing potential
  and locally defined reaction   A Robin boundary-value problem with non-homogeneous differential operator,
indefinite potential, and reaction defined only near zero is investigated. The
existence of one or more nodal solutions is achieved by using truncation,
perturbation, and comparison techniques, results from Morse theory, besides
variational methods.

37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci