Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Study of Antigravity in an F(R) Model and in Brans-Dicke Theory with
  Cosmological Constant   We study antigravity, that is having an effective gravitational constant with
a negative sign, in scalar-tensor theories originating from $F(R)$-theory and
in a Brans-Dicke model with cosmological constant. For the $F(R)$ theory case,
we obtain the antigravity scalar-tensor theory in the Jordan frame by using a
variant of the Lagrange multipliers method and we numerically study the time
dependent effective gravitational constant. As we shall demonstrate by using a
specific $F(R)$ model, although there is no antigravity in the initial model,
it might occur or not in the scalar-tensor counterpart, mainly depending on the
parameter that characterizes antigravity. Similar results hold true in the
Brans-Dicke model.

17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th