Explosive phenomena in modified gravity

TL;DR

This paper investigates how certain modified gravity models, proposed to explain cosmic acceleration, lead to rapid singularities in gravitating systems with increasing mass density, occurring much faster than the universe's age.

Contribution

It demonstrates that models of modified gravity can cause systems with rising mass density to reach singular states in a short time, highlighting potential physical instabilities.

Findings

Systems with increasing mass density evolve to infinite curvature scalar.

Singular states occur on timescales much shorter than cosmological time.

Modified gravity models may have observable implications for astrophysical systems.

Abstract

Observational manifestations of some models of modified gravity, which have been suggested to explain the accelerated cosmological expansion, are analyzed for gravitating systems with time dependent mass density. It is shown that if the mass density rises with time, the system evolves to the singular state with infinite curvature scalar. The corresponding characteristic time is typically much shorter than the cosmological time.