Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Monotonicity of the period function of the Li\'enard equation of second
  kind   This paper is concerned with the monotonicity of the period function for
closed orbits of systems of the Li\'enard II type equation given by $\ddot{x} +
f(x)\dot{x}^{2} + g(x) = 0$. We generalize Chicone's result regarding the
monotonicity of the period function to planar Hamiltonian vector fields in the
presence of a position dependent mass. Sufficient conditions are also given for
the isochronicity of the potential in case of such a system.

35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat