Physical interpretation of pp-waves with axial torsion

TL;DR

This paper explores generalized pp-waves with axial torsion in quadratic metric-affine gravity, revealing they form a broader class of solutions and relate to Einstein-Weyl theory, thus deepening understanding of gravitational and neutrino interactions.

Contribution

It introduces generalized pp-waves with axial torsion as new vacuum solutions and compares them to Einstein-Weyl solutions, expanding the landscape of gravitational models.

Findings

Generalized pp-waves with axial torsion are new vacuum solutions.

Classical pp-waves are a special case within a broader solution class.

Connections between torsion-based solutions and Einstein-Weyl theory are established.

Abstract

We consider generalised pp-waves with purely axial torsion, which we previously showed to be new vacuum solutions of quadratic metric-affine gravity. Our analysis shows that classical pp-waves of parallel Ricci curvature should not be viewed on their own. They are a particular representation of a wider class of solutions, namely generalised pp-waves of parallel Ricci curvature. We compare our pp-waves with purely axial torsion to solutions of Einstein-Weyl theory, the classical model describing the interaction of gravitational and massless neutrino fields.