Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Relaxation in stellar systems and the shape and rotation of the inner
  dark halo   Why do galactic bars rotate with high pattern speeds, when dynamical friction
should rapidly couple the bar to the massive, slowly rotating dark halo? This
longstanding paradox may be resolved by considering the dynamical interactions
between the galactic disk and structures in the dark halo. Dynamical friction
between small-scale halo structure and the disk spins up and flattens the inner
halo, thereby quenching the dynamical friction exerted by the halo on the bar;
at the same time the halo heats and thickens the disk, perhaps forming a
rapidly rotating bulge. Two possible candidates for the required halo
structures are massive black holes and tidal streamers from disrupted precursor
halos. More generally, gravitational scattering from phase-wrapped
inhomogeneities represents a novel relaxation process in stellar systems,
intermediate between violent relaxation and two-body relaxation, which can
isotropize the distribution function at radii where two-body relaxation is not
effective.

28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
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
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess