On the stress-energy tensor of a null shell in Einstein-Cartan gravity

TL;DR

This paper revisits the stress-energy tensor of null shells in Einstein-Cartan gravity, showing how torsion discontinuities influence its properties and differ from previous formulations.

Contribution

It introduces a consistent approach to torsion discontinuities that ensures the stress-energy tensor remains tangent to null hypersurfaces in Einstein-Cartan gravity.

Findings

Modified stress-energy tensor is tangent to the null hypersurface.

Proper torsion discontinuity choice aligns with antisymmetry of torsion tensor.

Differences from previous formulations are clarified.

Abstract

The stress-energy tensor of a matter shell whose history coincides with a null hypersurface in the Einstein-Cartan gravity is revisited. It is demonstrated that with a proper choice for the torsion discontinuity taken to be orthogonal to the null hypersurface and consistent with the antisymmetric property of torsion tensor, the modified expression for the asymmetric stress-energy tensor is automatically tangent to the hypersurface. The main differences with respect to a previous work are addressed