Gravitational collapse in Quadratic Gravity

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.