Viability of Arctan Model of f(R) Gravity for Late-time Cosmology
  $f(R)$ modifications of Einstein's gravity is an interesting possibility to explain the late time acceleration of the Universe. In this work we explore the cosmological viability of one such $f(R)$ modification proposed in (Kruglov:2013). We show that the model violates fifth-force constraints. The model is also plagued with the issue of curvature singularity in a spherically collapsing object, where the effective scalar field reaches to the point of diverging scalar curvature. 
Koushik Dutta, Sukanta Panda and Avani Patel
gr-qc astro-ph.CO hep-th