On the collapse in fourth order gravities

TL;DR

This paper investigates how fourth order gravity theories alter gravitational collapse dynamics, revealing deviations from General Relativity and identifying parameter constraints to exclude certain models.

Contribution

It analyzes the collapse process in fourth order gravity theories, highlighting the role of a new scalar mode and its impact on collapse time and model viability.

Findings

Higher initial contraction in fourth order theories

Collapse deviations depend on specific model parameters

Certain parameter regions can be ruled out based on collapse behavior

Abstract

The gravitational collapse in fourth order theories of gravity defined by an arbitrary action of the scalar curvature shows significant deviations with General Relativity. The presence of a new scalar mode produces a higher initial contraction that favors the reduction of the collapsing time. However, depending on the particular model, there are fundamental differences when the modifications to the General Relativity collapse leave the linear regime. These analyses can be used to exclude an important region of the parameter space associated with alternative gravitational models.