Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Singular Accelerated Evolution in Massive $F(R)$ Bigravity   The possibility to have singular accelerated evolution in the context of
$F(R)$ bimetric gravity is investigated. Particularly, we study two singular
models of cosmological evolution, one of which is a singular modified version
of the Starobinsky $R^2$ inflation model. As we demonstrate, for both models in
some cases, the slow-roll parameters become singular at the Type IV
singularity, a fact that we interpret as a dynamical instability of the theory
under study. This dynamically instability may be an indicator of graceful exit
from inflation and we thoroughly discuss this scenario and the interpretation
of the singular slow-roll parameters. Furthermore, it is demonstrated that for
some versions of $F(R)$ bigravity, singular inflation is realized in consistent
way so that inflationary indices are compatible with Planck data. Moreover, we
study the late-time behavior of the two singular models and we show that the
unified description of early and late-time acceleration can be achieved in the
context of bimetric $F(R)$ gravity.

27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat