Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cusps without chaos   We present cuspy, non-axisymmetric, scale-free mass models of discs, whose
gravitational potentials are of St\"ackel form in parabolic coordinates. A
black hole may be added at the centre, without in any way affecting the
St\"ackel form; the dynamics in these potentials is, of course, fully
integrable. The surface density, $\Sigma_{disc}\propto 1/r^{\gamma}$, where $0
<\gamma < 1$ corresponds to steep cusps for which the central force diverges.
Thus cusps, black holes, and non-axisymmetry are not a sure recipe for chaos,
as is generally assumed. A new family of orbits, lens orbits, emerges to
replace the box orbits of models of elliptical galaxies that have
constant-density cores. Loop orbits are conspicuous by their absence. Both
lenses and boxlets (the other family of orbits), can be elongated in the
direction of the density distribution, a property that is favourable for the
construction of non-axisymmetric, self-consistent equilibrium models of
elliptical galaxies.

29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th