An elliptic proof of the splitting theorems from Lorentzian geometry

We provide a new proof of the splitting theorems from Lorentzian geometry, in which simplicity is gained by sacrificing linearity of the d’Alembertian to recover ellipticity. We exploit a negative homogeneity (non-uniformly) elliptic $p$-d’Alembert operator for this purpose. This allows us to bring the Eschenburg, Galloway, and Newman Lorentzian splitting theorems into a framework closer to the Cheeger-Gromoll splitting theorem from Riemannian geometry.