Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Boundedness and persistence of delay differential equations with mixed
  nonlinearity   For a nonlinear equation with several variable delays $$
\dot{x}(t)=\sum_{k=1}^m f_k(t, x(h_1(t)),\dots,x(h_l(t)))-g(t,x(t)), $$ where
the functions $f_k$ increase in some variables and decrease in the others, we
obtain conditions when a positive solution exists on $[0, \infty)$, as well as
explore boundedness and persistence of solutions. Finally, we present
sufficient conditions when a solution is unbounded. Examples include the
Mackey-Glass equation with non-monotone feedback and two variable delays; its
solutions can be neither persistent nor bounded, unlike the well studied case
when these two delays coincide.

22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs