On the hypotheses of Penrose’s singularity theorem under disformal transformations Eduardo Bittencourt, Gabriel G. Carvalho, Iarley P. Lobo and Leandro Santana Eur. Phys. J. C, 80 3 (2020) 265 Published online: 24 March 2020 DOI: 10.1140/epjc/s10052-020-7830-0