Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the active gravitational mass of a non-spherical source leaving
  hydrostatic equilibrium   We obtain an expression for the active gravitational mass (Tolman) of a
source of the $\gamma$ metric, just after its departure from hydrostatic
equilibrium, on a time scale of the order of (or smaller than) the hydrostatic
time scale. It is shown that for very compact sources, even arbitrarily small
departures from sphericity, produce significant decreasing (increasing) in the
values of active gravitational mass of collapsing (expanding) spheres, with
respect to its value in equilibrium, enhancing thereby the stability of the
system.

3
The categories of this paper are: physics
2
The categories of this paper are: math
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga