Gravitational collapse in Quadratic Gravity

TL;DR

This paper investigates how quadratic gravity modifies gravitational collapse dynamics of a scalar field, revealing significant deviations from General Relativity while maintaining EFT validity, and discusses associated limitations and instabilities.

Contribution

It introduces an order reduction method to simulate collapse in quadratic gravity within EFT limits, highlighting deviations from GR and analyzing stability issues.

Findings

Solutions show significant curvature deviations from GR.

EFT remains valid during collapse scenarios.

Instabilities and limitations of the approach are identified.

Abstract

This study explores the gravitational collapse of a massless scalar field within Quadratic Gravity treated as a dimension-four operator Effective Field Theory extension to General Relativity. The additional degrees of freedom associated with the higher derivatives in this theory are removed by an Order Reduction approach, where the truncated expansion nature of the theory is exploited. Through simulations, we find scenarios where solutions remain within the bounds of the Effective Field Theory while displaying significant deviations from General Relativity in the dynamics of curvature invariants during the collapse. Limitations of the approach taken, the Effective Field Theory approximation, and the appearance of instabilities are also discussed.