Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Preserving general physical properties in model reduction of dynamical
  systems via constrained-optimization projection
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn