Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: T-comitants and the Problem of a Center for Quadratic Differential
  Systems   The new necessary and sufficient affine invariant conditions for the
existence and for determining the number of centers for general quadratic
system are pointed out. These conditions correspond to the partition of
12-dimensional coefficient space of indicated system with respect to the number
and the multiplicity of its finite critical points.

19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th