Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Entropy, Duality and Cross Diffusion   This paper is devoted to the use of the entropy and duality methods for the
existence theory of reaction-cross diffusion systems consisting of two
equations, in any dimension of space. Those systems appear in population
dynamics when the diffusion rates of individuals of two species depend on the
concentration of individuals of the same species (self-diffusion), or of the
other species (cross diffusion).

35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin