Review of gravitational wave solutions in quadratic metric-affine gauge gravity

Abstract

In this paper, we consider the quadratic Metric-Affine Gauge gravity Lagrangian, which contains all the algebraic invariants up to quadratic order in torsion, nonmetricity and curvature. The goal is to collect the known exact solutions for this theory that describe the propagation of a gravitational wave and some useful properties. We concentrate on solutions whose connections are different from the Levi-Civita one and provide also the extension of already known axial torsion solutions to more general Lagrangians. In the end, we will briefly discuss colliding waves and Riemannian solutions.