The paper “The Hawking-Penrose singularity theorem for C(1,1)-Lorentzian metrics” co-authored by Melanie Graf (Vienna), James D.E. Grant, Michael Kunzinger (Vienna), and Roland Steinbauer (Vienna), has been published in Communications in Mathematical Physics. A link to the published paper is here. The paper shows that the H-P singularity theorem continues to hold for Lorentzian metrics that have C(1,1) regularity.  The proof requires a detailed analysis of the matrix Riccati equation for the approximating metrics, which may be of independent interest.