Spherical Collapse in f(R) Gravity

TL;DR

This paper uses numerical simulations to study spherical collapse in f(R) gravity, revealing unique density enhancements and challenging existing analytical models, with implications for understanding cosmic structure formation.

Contribution

It introduces a numerical relaxation scheme to simulate nonlinear spherical collapse in f(R) gravity, highlighting phenomena not captured by previous analytical approximations.

Findings

Enhanced density near the virial radius observed

Analytical models fail to fully describe nonlinear collapse

Collapse time estimates inform halo mass function calculations

Abstract

We use 1-dimensional numerical simulations to study spherical collapse in the f(R) gravity models. We include the nonlinear coupling of the gravitational potential to the scalar field in the theory and use a relaxation scheme to follow the collapse. We find an unusual enhancement in density near the virial radius which may provide observable tests of gravity. We also use the estimated collapse time to calculate the critical overdensity $\delta_c$ used in calculating the mass function and bias of halos. We find that analytical approximations previously used in the literature do not capture the complexity of nonlinear spherical collapse.