Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Representation of rational positive real functions of several variables
  by means of positive long resolvent   A rational homogeneous (of degree one) positive real matrix-valued function
is presented as the Schur complement of a block of the linear pencil with
positive semidefinite matrix coefficients. The partial derivative numerators of
a rational positive real function are the sums of squares of polynomials.

20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin