Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Scaling Cosmology   We show that with the help of a suitable coupling between dark energy and
cold dark matter it is possible to reproduce any scaling solution $\rho
_{X}\propto \rho_{M}a^{\xi}$, where $\rho_{X}$ and $\rho_{M}$ are the densities
of dark energy and dark matter, respectively. We demonstrate how the case $\xi
= 1$ alleviates the coincidence problem. Future observations of supernovae at
high redshift as well as quasar pairs which are planned to discriminate between
different cosmological models will also provide direct constraints on the
coupling between dark matter and dark energy.

22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat