Curing singularities in cosmological evolution of F(R) gravity

Understand

We study $F(R)$ modified gravity models which are capable of driving the accelerating epoch of the Universe at the present time whilst not destroying the standard Big Bang and inflationary cosmology.

• Recent studies have shown that a weak curvature singularity with $|R|\to\infty$ can arise generically in viable $F(R)$ models of present dark energy (DE) signaling an internal incompleteness of these models.
• In this work we study how this problem is cured by adding a quadratic correction with a sufficiently small coefficient to the $F(R)$ function at large curvatures.
• At the same time, this correction eliminates two more serious problems of previously constructed viable $F(R)$ DE models: unboundedness of the mass of a scalar particle (scalaron) arising in $F(R)$ gravity and the scalaron overabundance problem.