Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Is flat rotation curve a sign of cosmic expansion?   Four alternative proposals as the possible solutions for the rotation curve
problem are introduced on the basis of assumption that the cosmic expansion is
engaged with the galactic dynamics over the halo. The first one proposes a
modification of equivalence principle in an accelerating universe. The second
one proposes a modification of Mach principle in an expanding universe. The
third one proposes a dynamics of variable mass system for the halo in an
expanding universe, and the fourth one proposes the replacement of physical
radius with comoving one over the halo, in an expanding universe.

2
The categories of this paper are: math
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph