Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Matter couplings in Horava-Lifshitz and their cosmological applications   In this paper, the issue how to introduce matter in Ho\v{r}ava-Lifshitz
theories of gravity is addressed. This is a key point in order to complete the
proper definition of these theories and, what is very important, to study their
possible phenomenological implications. As is well known, in
Ho\v{r}ava-Lifshitz gravity the breakdown of Lorentz invariance invalidates the
usual notion of minimally coupled matter. Two different approaches to bypass
this problem are here described. One is based on a Kaluza-Klein
reinterpretation of the 3+1 decomposition of the gravity degrees of freedom,
what naturally leads to a definition of a U(1) gauge symmetry and, hence, to a
new type of minimal coupling. The other approach relies on a midi-superspace
formalism and the subsequent parametrization of the matter stress-energy tensor
in terms of deep infrared variables. Using the last option, the phase space of
the Horava-Lifshitz cosmology in the presence of general matter couplings is
studied. It is found, in particular, that the equation of state of the
effective matter may be very different from the actual matter one, owing to the
non-linear interactions which exists between matter and gravity.

37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph