The unphysical character of minimally coupled dark energy fluids Ronaldo C. Duarte, Edésio M. Barboza, Everton M. C. Abreu and Jorge Ananias Neto Eur. Phys. J. C, 79 4 (2019) 356 Published online: 24 April 2019 DOI: 10.1140/epjc/s10052-019-6876-3