Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitation and spatial conformal invariance   It is well-known that General Relativity with positive cosmological constant
can be formulated as a gauge theory with a broken SO(1,4) symmetry. This
symmetry is broken by the presence of an internal space-like vector $V^A$,
$A=0,...,4$, with SO(1,3) as a residual invariance group. Attempts to ascribe
dynamics to the field $V^{A}$ have been made in the literature but so far with
limited success. Regardless of this issue we can take the view that $V^A$ might
actually vary across spacetime and in particular become null or time-like. In
this paper we will study the case where $V^A$ is null. This is shown to
correspond to a Lorentz violating modified theory of gravity. Using the
isomorphism between the de Sitter group and the spatial conformal group,
$SO(1,4)\simeq C(3)$, we show that the resulting gravitational field equations
are invariant under all the symmetries, but spatial translations, of the
conformal group C(3).

1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph