On the hypotheses of Penrose’s singularity theorem under disformal transformationsEduardo Bittencourt, Gabriel G. Carvalho, Iarley P. Lobo and Leandro SantanaEur. Phys. J. C, 80 3 (2020) 265DOI: https://doi.org/10.1140/epjc/s10052-020-7830-0