Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Enhanced Big Rip without Conventional Dark Energy   A modified Friedmann equation which arises in an extension of general
relativity which accommodates a time-dependent fundamental length $L(t)$ leads
to cosmological models where the scale factor diverges with an essential
singularity at a finite future time. Such models have no dark energy in the
conventional sense of energy possessing a truly simple pressure-energy
relationship. Data on supernovae restrict the time from the present until the
Rip to be generically longer than the current age of the Universe.

9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
1
The categories of this paper are: cs