Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Revisiting f(R) gravity models that reproduce $\Lambda$CDM expansion   We reconstruct an $f(R)$ gravity model that gives rise to the particular
$\Lambda$CDM background evolution of the universe. We find well-defined,
real-valued analytical forms for the $f(R)$ model to describe the universe both
in the early epoch from the radiation to matter dominated eras and the late
time acceleration period. We further examine the viability of the derived
$f(R)$ model and find that it is viable to describe the evolution of the
universe in the past and there does not exist the future singularity in the
Lagrangian.

32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph