Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topics in the theory of positive solutions of second-order elliptic and
  parabolic partial differential equations   The purpose of the paper is to review a variety of recent developments in the
theory of positive solutions of general linear elliptic and parabolic equations
of second-order on noncompact Riemannian manifolds, and to point out a number
of their consequences.

19
The categories of this paper are: eess
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int