Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the role of the far fields and of cosmology for the theory of
  gravitation and for the dark matter problem   We give an estimate of the gravitational field of force exerted on a test
particle by the far galaxies, in the frame of the weak field approximation. In
virtue of Hubble's law, the action of the far matter turns out to be non
negligible, and even the dominant one. An extremely simplified cosmological
model is considered. A nonvanishing contribution is obtained only if the
discrete and fractal nature of the matter distribution is taken into account.
The force per unit mass acting on a test particle is found to be of the order
of $0.2 cH_0$, where $c$ is the speed of light and $H_0$ the present value of
Hubble's constant.

5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex